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CHY Flashcards

High yield

1
Q

95% confidence intervals

A

Range of values that is 95% likely to contain the true value

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2
Q

Standard deviation

A

Value that shows how much variation there is from the mean

  • 68% of values in dataset lies between -/+ 1 SD
  • 95% between 2SD
  • 99.7% between 3SD
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3
Q

P value

A

Likelihood that the observed result is due to change

P > 0.05 is not statistically significant

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4
Q

Odds ratio

A

Ratio of odds that something will happen, to the odds that it won’t happen.

Used in case control studies.

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5
Q

Blinding

A

Patients/clinicians/researchers are prevented from knowing certain information that may lead to conscious or subconscious bias on their part

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6
Q

Concealment of allocation

A

The procedure for protecting the randomisation process

Person randomising the patient does not know what the treatment allocation will be

Prevents selection bias affecting which patients are give which treatment (the bias the randomisation is designed to avoid)

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7
Q

Intention to treat analysis

A

Analysis based on the initial treatment intended from allocation,

Intention to treat (ITT) analysis means all patients who were enrolled and randomly allocated to treatment are included in the analysis and are analysed in the groups to which they were randomized, not the treatment eventually administered.

I.e. “once randomized, always analyzed”

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8
Q

Treatment fidelity

A

How accurately the intervention is reproduced from a manual, protocol or model

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9
Q

Number needed to treat

NNtT

A

Number of patients that are needed to be treated with the experimental therapy to prevent one negative outcome

E.g. After myocardial infarction, 18 people need to take an angiotensin-converting enzyme (ACE) inhibitor to prevent one heart attack (NNT = 18)

It is defined as the inverse of the absolute risk reduction.

1/Absolute risk reduction

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10
Q

Purpose of randomisation?

A

To try and ensure that any characteristics of the sample population that may affect the results (confounders) are distributed equally between the 2 study groups, and avoid selection bia

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11
Q

Which type of studies are often affected by recall bias?

A

Case control

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12
Q

What is recall bias?

A

The participant either cannot remember back to when they were exposed or their outcome changes their perception of the exposure

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13
Q

Internal validity

A

Accuracy

How well the study was conducted.

Taking confounders into account and removing bias.

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14
Q

External validity

A

Generalisability

How well it can be applied to different scenarios, patients, environments.

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15
Q

List 4 methods that can be used to limit confounding variables.

(may be used in cohort studies!)

A

Restriction:

  • Limit participants of study that have possible confounders
  • Means less data available
  • This method can be difficult with multiple confounders

Matching:

  • Make comparison groups (with and without the confounder)
  • Used for things like age and sex in case-control studies

Stratification:

  • Analyse exposure with sub-groups of the confounder
  • Adjust for confounding (if there are few variables)
  • Recombine data
  • Means sometimes these subgroups have very few participants in them

Multiple variable regression:

  • Coefficients are established for the confounder groups
  • Allows for better adjustment
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16
Q

Case-control studies are prone to recall bias in general

A

Cohort studies are prone to selection bias in general

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17
Q

Population attributable risk (PAR)

A

The portion of the incidence of a disease in the population (exposed and non-exposed) that is due to exposure

It is the incidence of a disease in the population that would be eliminated if the cause of exposure was eliminated

This can be expressed as a value or percentage

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18
Q

Allocative efficiency

A

Investing in worthwhile interventions

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19
Q

Technical efficiency

A

Investing in the interventions that make the best use of scarce resources

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20
Q

SPIKES

A 
Setting
Perception
Invitation
Knowledge
Empathy
Summary
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21
Q

Kubler-Ross model of grief

A 
Denial
Anger
Bargaining
Depression
Acceptance
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22
Q

Bowlby model of grief

A

Numbing
Yearning/searching
Disorganisation
Reorganisation

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23
Q

Most common cancers in men

A 
Lung
Prostate
Colorectal
Stomach
Liver
Bladder
Oesophagus
Non-Hodgkin
Kidney
Leukaemia
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24
Q

Most common cancers in women

A 
Breast
Lung
Colorectal
Cervical
Thyroid
Uterine
Stomach
Ovarian
Liver
Non-Hodgkin
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25
Q

Most common cancers in children

A

Leukemia
Brain
Lymphoma
Soft tissue sarcoma

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26
Q

Type I error

A

False positive

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27
Q

Type II error

A

False negative

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28
Q

Standardised mortality ratio (SMR)

A

Ratio between the observed number of deaths (O) in a study population to the number of expected deaths (E)

SMR = O/E

The rate of deaths in one population compared with national averages corrected for age, sex, social class, etc.?

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29
Q

Direct standardisation in the context of death rates?

A

Age is major conounding factor in death rates

Direct standardisation requires that we know the age-specific rates of mortality in all populations under study

  • Weighted average if stratum-specific rates
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30
Q

Indirect standardisation in the context of death rates?

A

Age is major conounding factor in death rates

Indirect standarisation only requires that we know the total number of deaths and the age structure of the study population

  • How many deaths would we expoect in age group?
  • How many were there?
  • Work outobserved/expected mortality rate
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31
Q

When is indirect standardisation preferable?

A

Small numbers in particular age groups

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32
Q

Likelihood ratio

A

The likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that the same result would be expected in a patient without the target disorder

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33
Q

Length bias

A

Overestimation of survival duration among screening-detected cases by the relative excess of slowly progressing cases

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34
Q

Consequences of length bias?

A

 Diseases with a longer sojourn time are ‘easier to catch’ in the screening net.

 On average, individuals with disease detected through screening ‘automatically; have a better prognosis than people who present with symptoms/signs.

 If we simply compare individuals who choose to by screened with those who don’t we will get a distorted picture.

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35
Q

Lead time bias

A

Overestimation of survival duration among screen-detected cases (relative to those detected by signs + symptoms) when survival is measured from diagnosis

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36
Q

Consequences of lead time bias?

A

 Survival is inevitably longer following diagnosis through screening because of the ‘extra’ lead time

 Because of this the appropriate measure of effectiveness is deaths prevented, not survival

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37
Q

Over-diagnosis bias?

A

 Overestimation of survival duration among screen-detected cases caused by inclusion of pseudodisease - subclinical disease that would not become overt before the patient dies of other causes.

 Occurs when screen-detected cancers are either non-growing or so slow-growing that they never would cause medical problems

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38
Q

Statutes (laws) that oblige doctors to disclose information

A

 Public Health Act 1984
 Road Traffic Act 1988
 Prevention of terrorism act 1989

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39
Q

3 different types of errors

A

 Knowledge based - Such as forming wrong intentions or plans as a result of inadequate knowledge/experience

 Rule based - Encounter relatively familiar problem but apply wrong rule, either misapplication of a good rule or application of a bad rule.

 Skills based - Attention slips and memory lapses, involve the unintended deviation of actions from what may have been a good plan. We are all prone to these types of errors, mainly due to interruption and distractions.

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40
Q

Latent error

A

 Develop over time until they combine with other factors or active failures to cause an adverse event

 Long lived and often can be identified and removed before they cause an adverse event

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41
Q

What are violations?

A

 Deliberate deviation from some regulated code of practice or procedure

 They occur because people intentionally break the rules

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42
Q

List 4 types of violations

A

 Routine - Regularly performed shortcuts due to system, process or task being poorly designed or actions. May become tacitly accepted practice over time

 Reasoned - Occasional reasoned deviation from a protocol or procedure which we believe we have good reason for making (e.g. time constraints), may be in patient’s best interests

 Reckless - Deliberate deviations from a protocol/code of conduct and include acts where opportunity for harm is foreseeable and ignored, although harm may never be intended

 Malicious - Deliberate deviations from a protocol/code of conduct, where the intention is to cause harm

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43
Q

What is a near miss?

A

A situation in which events arise during clinical care but fail to develop further

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44
Q

Swiss cheese model of accident causation

A

Although many layers of defence lie between hazards and accidents, there are flaws in each layer that, if aligned, can allow the accident to occur.

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45
Q

Main causes of individual vs system errors?

A

Individual error - Errors of individuals, blames individual for forgetfulness, inattention or moral weakness

System error - Conditions under which an individual works, tries to build defences to eliminate errors or mitigate their effect

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46
Q

List 3 antenatal screening tests that identify major abnormalities

A

 Alpha fetoprotein - Raised in neural tube defects and some GI abnormalities

 Downs test - Alpha fetoprotein and HCG

 Ultrasound - Growth check, cardiac abnormalities, diaphragmatic hernia

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47
Q

Neonatal tests

A

Blood spot test:

  • PKU
  • Cystic fibrosis
  • Sickle cell disease
  • Congenital hypothyroidism

Physical examination

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48
Q

4 types of neglect

A

 Physical neglect
 Educational neglect
 Emotional neglect
 Medical neglect

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49
Q

Which act says 16 year old has full capacity?

A

The family law reform act 1969

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50
Q

What is Gillick competency?

A

Child (under 16) can consent to medical treatment if deemed competent by medical professional, without need for parental permission or knowledge

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51
Q

What are the Fraser guidelines?

A

Doctor can give contraceptive advice and treatment to a person under 16 if she is mature and intelligent, likely to continue to have sex, and if the treatment if in her best interests

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52
Q

Effects of targeting population for prevention?

A

 Large potential benefit to community

 Low potential benefit to individual

 May be low perceived benefit to individual

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53
Q

Effects of targeting high risk groups for prevention?

A

 Larger potential benefit to individual

 Smaller effect on population rate of stroke

 Many of the conditions you treat are asymptomatic

 May of the treatments have side effects

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54
Q

What did the PROGRESS trial show?

A

Reducing blood pressure after stroke reduces risk of stroke recurrence

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55
Q

Occupational causes of asthma

A

Bakers
Welders
Paint sprayers
Laboratory workers

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56
Q

Occupational causes of COPD

A 
Coal mining
Agriculture
Construction
Dock workers
Brick making
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57
Q

Simple coal worker’s pneumoconiosis

A

 After around 10 years coal mining, small nodules are present

 Shouldn’t cause major impairment in lung function

 Some coal workers have symptoms of chronic bronchitis (cough)

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58
Q

Pneumoconiosis

A

Occupational restrictive lung disease caused by inhalation of dust (coal dust, silica, asbestos)

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59
Q

Silicosis

A

Occupational lung disease caused by inhalation of crystalline silica dust, and is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lung.

It is a type of pneumoconiosis.

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60
Q

2 types of asbestos fibres

A

Serpentine - Curly, white asbestos (relatively harmless), cleared with mucociliary escalator

Amphiboles - Short, sharp, blue/brown asbestos (have malignant potential)

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61
Q

What are preference sensitive and probability sensitive decisions?

A

Preference sensitive - The person might feel strongly about the side effects of the treatment

Probability sensitive - Sensitive to changes in the chance of different outcomes

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62
Q

Clinical decision support systems (CDSS) are designed to aid clinician decision making

A

 Computerised
 Paper based
 Reminder systems
 Developed to aid with particular decisions

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63
Q

Examples of CDSS

A

 Reminder systems - Screening, vaccination, testing, medication use

 Decision systems (diagnosis and treatment) - Model individual patient data against
epidemiological data

 Prescribing - Advice on drug and dosage, highlights potential drug interactions

 Condition management - Assists monitoring patients

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64
Q

Equity in financing

A

Geographic allocation of funding by weighted capitation

Resourcing determined by population weighted by need

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65
Q

What is class equality/inequality in health care?

A

Evidence of social class equality in the use of primary care and social class inequality in the use of secondary care

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66
Q

What is efficiency?

A

Target resources to those activities that give the greatest health gain for the money spent as this will maximise population health gain

Informing these choices required estimation of value of what is given up when a patient is treated (opportunity cost) and the value of what is gained in terms of improvements in the health of patients

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67
Q

Fair-innings arguement (1997)

A

Older people have had a long life already, therefor fairer to divert resources to younger people

Elderly also have a disproportionate share of the available resources allocated to them

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68
Q

Contradictions for the Fair-innings argument?

A

Treating on the basis of need might mean older people don’t receive lower priority

Years of life saved shouldn’t matter, the quality of life is more important e.g QALYs

Fairness is not the only thing that matters, other things do too e.g equal treatment

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69
Q

Advantages of cohort studies

A

 Good for rare risk factors
 Can assess multiple risk factors at once
 Yields true incidence rates and relative risk
 Best for common diseases

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70
Q

Disadvantages of cohort studies

A

 Expensive compared to case-control studies
 Time consuming - Risk factor may take decades to cause disease (long latency period)
 Not good for rare diseases
 Confounding factors
 Cannot determine odds ratio

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71
Q

Advantages of case-control studies

A 
 Good for rare diseases
 Good for tracing source of an outbreak
 Relatively inexpensive and quick compared to cohort studies
 Yields odds ratios
 Good for long latency periods
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72
Q

Disadvantages of case-control studies

A 
 Relies on recall or existing records
 Inferior to cohort
 Cannot determine relative risk directly
 Not good for rare exposures
 Selection of controls difficult
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73
Q

What should systematic reviews have in their inclusion criteria?

A

 Papers that have not been published (publication bias)

 Papers that are not in English

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74
Q

R0

A

Basic reproduction rate

The average number of individuals directly infected by an infectious case during the infectious period, in a totally susceptible population (number of secondary cases following introduction of infection)

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75
Q

What factors affect R0?

A

The rate of contacts in the host population

The probability of infection being transmitted during contact

The duration of infectiousness

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76
Q

Effective reproduction rate (R)

A

Estimates the average number of secondary cases per infectious case in a population made up of both susceptible and non-susceptible hosts

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77
Q

Equation for effective reproduction rate

A

R = R0x (x is the fraction of the host population which is susceptible e.g. half population is 0.5)

R>1 - number of cases increases

R<1 - Number of cases decreases, needs to be maintained for elimination

R=1 - Epidemic threshold

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78
Q

Herd immunity equation

A

H = (R0-1)/ R0

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79
Q

What are some of the free and private travel vaccines available?

A

Free - Diptheria, polio, tetanus, typhoid, hepatitis A, cholera

Private - Hepatitis B, japanese encephalitis, meningitis, rabies, TB, yellow fever

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80
Q

Define disability

A

Restriction or lack (resulting from an impairment) of ability to perform an activity in the manner or within the range considered normal for human being

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81
Q

Dual process model

A

 Better model that says we cope w/ grief/bad things by carrying out loss orientated + restoration oriented behaviours

 Loss oriented: grief work, breaking bonds, denial

 Restoration orientated: doing new things new roles + relationships

 These 2 processes occur simultaneously through everyday life experiences

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82
Q

What different forms can the stress response take?

A
  1. Direct action
  2. Seeking information
  3. Doing nothing
  4. Developing way of coping
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83
Q

Likelihood ratio

A

The likelihood that a given test result would be expected in a patient with the target disorder compared to the likelihood that that same result would be expected in a patient without the target disorder.

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84
Q

What is the likelihood ratio for positive test results?

LR+

A

Chance of testing positive if you have disease/ chance of testing positive if you don’t have disease

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85
Q

What is the LR for negative test results?

LR-

A

Chance of testing negative if you have disease/ chance of testing negative if you don’t have disease

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86
Q

What is the significance of LR+ and LR-?

A

The larger the LR+ the greater chance you have disease if your test is positive

The smaller the LR- the less chance you have disease if your test is negative

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87
Q

What is the pre-test probability?

A

Chances of disease before test = the disease prevalence in your population

88
Q

Length bias

A

Screening is best at picking up long-lasting and slowly-progressive conditions rather than rapidly-progressing poor prognostic ones

Overestimation of survival duration among screening-detected cases by the relative excess of slowly progressing cases

Consequences:
 Diseases with a longer sojourn time are ‘easier to catch’ in the screening net.
 On average, individuals with disease detected through screening ‘automatically; have a better prognosis than people who present with symptoms/signs.
 If we simply compare individuals who choose to by screened with those who don’t
we will get a distorted picture.

89
Q

Lead time bias

A

Overestimation of survival duration among screen-detected cases (relative to those detected by signs and symptoms) when survival is measured from diagnosis.

Consequences:
 Survival is inevitably longer following diagnosis through screening because of the ‘extra’ lead time
 Because of this the appropriate measure of effectiveness is deaths prevented, not survival

90
Q

Overdiagnosis bias?

A

 Overestimation of survival duration among screen-detected cases caused by inclusion of pseudodisease - subclinical disease that would not become overt before the patient dies of other causes.

 Occurs when screen-detected cancers are either non-growing or so slow-growing that they never would cause medical problems

91
Q

How can waiting lists be measured?

A 
Average or median waiting time
Average or median wait of those on list
Number on the list (size)
Proportion waiting more than x days
Proportion of those on list waiting more than x days
Time to clear list
92
Q

Identify two potential disadvantages to individuals or to society that may result from the introduction of a screening programme

A

False positive results leading to anxiety and unnecessary interventions.

Opportunity cost of the programme for NHS (and individual).

Increased diagnostic activity.

93
Q

How might measuring BMI in school children be used?

A

Overweight (or underweight) children are identified and parents take appropriate action.

Schools take action to tackle obesity

The importance of obesity is highlighted in the community
NHS and/or Local Authority have information that can be used to plan services to tackle obesity

Local obesity figures and performance can be monitored

94
Q

What conditions are screened for in newborns?

A

Congenital hypothyroidism;

Phenylketonuria;

Medium Chain Acetyl Decarboxylase (MCAD);

Hearing problems;

Cystic fibrosis;

Sickle cell disease;

95
Q

Give five examples of the problems faced by families affected by AIDS in low income countries.

A 
Children as care givers
Orphans
Psychosocial distress
Poverty
Lack of schooling
Reduced access to health care services
Discrimination
Child labour and exploitation
Sexual exploitation
Street children
96
Q

HIV/AIDS in Africa is changing the pattern of the population structure.

What is the effect of the changes on the age structure and why should it have this effect?

A

Reduction in the young and middle aged adults rather than children (2 marks)

Infects sexually active people with an approx. 10 year period to death so time to reproduce is not affected (2 marks)

97
Q

Where in Africa does HIV/AIDS have most impact?

A

Sub-Saharan

98
Q

Give two reasons why waiting times may benefit the NHS.

A

Act as rationing

Makes best use of resources

99
Q

Give four initiatives taken in the NHS to reduce waiting lists which might come into your discussion.

A

More doctors/healthcare staff

Day cases

Targets and penalties for missing them

Activity based remuneration for doctors

Activity based remuneration for hospitals

Star ratings

Other service providers (e.g. contracting with private providers; switch to primary care provision)

100
Q

What was the outcome of the midwives’ act (1902)?

A

 Established normality in childbearing as the midwife’s role - Refer to doctors as soon as abnormality occurs

 This ensures equal access to midwives and doctors for childbearing women of all socioeconomic standing

101
Q

Benefits of institutionalised childbirth?

A

 Standardisation of care
 Access to good facilities to support childbirth
 Availability of populations of childbearing women and infants for the purposes of midwifery and obstetric training
 Faster access to emergency care
 Access of effective obstetric analgesia

102
Q

Risks of institutionalised childbirth?

A 
 Medicalisation
 Deposonalisation of birth
 Lack of privacy
 Inflexibility in labour and birth practices
 Limitation of resources
103
Q

What are the legal aspects of ART?

What act is it laid out in?

A

Human fertilisation and embryology authority act 2008

  • Welfare of child needs to be taken into account
  • Need for ‘supportive parenting’ hence valuing role of all (hetero and homo) parents
  • Sex selection/social selection of embryos is prohibited
104
Q

Standardised mortality ratio?

A

Ratio between the observed (O) number of deaths in a study population to the number of expected (E) deaths

SMR = O/E

105
Q

How can NHS reduce waiting times?

A

 Manage demand - Ensuring each referral represents the most appropriate decision for the care of the individual patient

 Manage the queue - Ensuring waiting lists are well managed and patients are called for treatment in appropriate order

 Manage capacity - Providing efficient and effective services that meet the level of demand from appropriate referrals

 Provide leadership - Ensuring that all parts of the local NHS work together to achieve waiting time improvements in the best interests of patients.

106
Q

Possible criteria for priority on waiting lists?

A 
 Clinical urgency
 Clinical severity
 Potential health gain
 Productivity and economic loss
 Equity waiting e.g. poverty
 Length of time waiting
107
Q

What does the NICE guidelines state about acupuncture in lower back pain, osteoarthritis, and headaches?

A

 Low back pain - Consider manual therapy, do not offer acupuncture

 Osteoarthritis - Manipulation and stretching should be considered as an adjunct to
core treatments, do not offer acupuncture

 Headache/migraine - Consider a course of up to 10 sessions of acupuncture over 5-8
weeks

108
Q

According to the mental capacity act 2005, a person lacks capacity if they are unable to …

A

 Understand information that may be relevant to the decision, including the consequence

 Retain information, even for a short time

 Use or weigh information to make decisions

 Communicate decision

109
Q

Type 1 error (false positive)

A

The null hypothesis is REJECTED when it is true

i.e. Showing a difference between two groups when it doesn’t exist, a false positive. This is determined against a preset significance level (termed alpha).

As the significance level is determined in advance the chance of making a type I error is not affected by sample size. It is however increased if the number of end-points are increased. For example if a study has 20 end-points it is likely one of these will be reached, just by chance.

110
Q

Type 2 error (false negative)

A

The null hypothesis is ACCEPTED when it is false.

i.e. Failing to spot a difference when one really exists, a false negative.

The probability of making a type II error is termed beta. It is determined by both sample size and alpha

111
Q

Risk

A

Probability of an event in a given time period.

112
Q

Risk ratio

A

Ratio of the probability of an event (risk) between two groups.

1 indicates risk is the same.

Used in cohort studies.

Risk ratio = Risk exposed/ Risk unexposed

Risk ratio = Risk of CVD smoker/Risk of CVD non smoker

113
Q

Population attributable risk?

A

The risk of disease will increase as the exposure prevalence or relative risk increases

114
Q

Main risk factors associated with lung cancer?

A 
 Smoking (90%)
 Radon
 Asbestos
 Environmental tobacco exposure
 Genetics
 Other lung diseases
 Prior radiation in chest area
115
Q

Different types of lung cancer?

A

 Small cell (13%)

 Non-small cell (87%)

  • Adenocarcinoma (>40%),
  • Squamous cell carcinoma (20%),
  • Large cell carcinoma (2%)

 Mesotheloma

116
Q

Prevention paradox

A

A preventive measure that brings large benefits to the community offers little to each participating individual

117
Q

How are confounding factors limited?

A

Restriction

  • Limit the participants of your study who have possible confounders
  • Means that you have less data and difficult with multiple confounders

Matching

  • Create a comparison group that is matched on the possible confounder, make case and control group as similar as possible on the confounder and then ask about exposure status
  • Used for strong confounders like age and sex

Stratification

  • Analyse exposure:outcome association in different subgroups of the confounder, recombine data and use a weighted average of the strata
  • Limitations : to take into account all confounders would require lots of strata and you may run out of data to fill all possible options in your strata

Multiple variable regression

  • You can adjust for the effects of multiple confounders, try and produce a linear model between the outcome and the different exposures
  • Allows for adjustment of estimates for confounding
118
Q

Types of research ethics committees?

A

 NHS Research ethics committees
 Higher Education Institution (HEI) research ethics committees
 Gene therapy advisory committee
 Social care research ethics committee
 Ministry of defence research ethics committee

119
Q

What was the Calman-Hine report?

A

Examined cancer services in the UK, and proposed a restructuring of cancer services to achieve a more equitable level of access to high levels of expertise throughout the country.

120
Q

What are the stages in the transtheoretical model?

A

Precontemplation
- No recognition of need/or interest in change

Contemplation
- Thinking about changing

Preparation
- Planning the change

Action
- Adopt new habits

Maintenance
- Active practice of new healthier behaviour

121
Q

How can utility be assessed?

A

Quality adjusted life year (QALY)

Standard gamble - Assesses utility for a health state by asking how high a risk of death would accept to improve it.

Time-trade off - Utility assessed by asking how much time (life expectancy) would give up to improve it

122
Q

What is restriction?

A

To manage confounding, limiting participant of study who have possible confounders.

Means you have less data

123
Q

What is matching?

A

Creating a comparison group that is matched on possible confounder.

Used for strong confounders like age and sex

124
Q

What is stratification?

A

Analyse exposure:outcome association in different subgroups. e.g. CHD in pie eaters v non-pie eaters

125
Q

5 ways to limit confounding variables?

A 
Restriction
Matching
Stratification
Multiple variable regression
Standardisation
126
Q

What is multiple variable regression?

A

Adjusting for the effects of multiple confounders, producing a linear model between outcome and different exposures

127
Q

What is standardisation?

A

To limit confounding, usually for age.

Comparing 2 groups in age subgroups

128
Q

What is standardised mortality ratio?

A

Comparing how many deaths you would expect to how many there actually were.

SMR > 100% = higher death than average.

This is an example of indirect standardisation

129
Q

Equation for risk ratio

A

Risk in exposure / Risk in unexposed

RR = a/a+c divided by c/c+d

130
Q

What is attributable risk (AR) aka risk difference?

A

Attributable risk (AR) or risk difference is the difference between the incidence rates in exposed and non-exposed groups.

In a cohort study, AR is calculated as the difference in cumulative incidences (risk difference) or incidence densities (rate difference).

This reflects the absolute risk of the exposure or the excess risk of the outcome (e.g. disease) in the exposed group compared with the non-exposed group.

AR is sometimes referred to as attributable risk in the exposed because it is used to quantify risk in the exposed group that is attributable to the exposure.

131
Q

What is absolute risk reduction?

A

In general, absolute risk reduction is the difference between one treatment comparison group’s event rate (EER) and another comparison group’s event rate (CER).

The difference is usually calculated with respect to two treatments A and B, with A typically a drug and B a placebo.

ARR = c/(c+d) - a/(a+b)

132
Q

Pre-test probability is equivalent to the prevalence of a condition

A

The proportion of people with the target disorder in the population at risk at a specific time (point prevalence) or time interval (period prevalence)

For example, the prevalence of rheumatoid arthritis in the UK is 1%

133
Q

Which one of the following is the best definition of the p value?

A. The probability of obtaining a similar result, assuming that the null hypothesis is true

B. The probability that a replicating experiment would not yield the same conclusion

C. The probability of obtaining a result at least as extreme, assuming that the null hypothesis is true

D. The probability that the null hypothesis is true

E. The probability of obtaining a result at least as extreme, assuming that the null hypothesis is false

A

C. The probability of obtaining a result at least as extreme, assuming that the null hypothesis is true

The p value is the probability of obtaining a result by chance at least as extreme as the one that was actually observed, assuming that the null hypothesis is true. It is therefore equal to the chance of making a type I error (see below).

134
Q

When does a type 2 error occur?

The null hypothesis is ACCEPTED when it is false.

A

A type II error occurs when the sample size in a study is too small to allow for a difference to be detected.

A type II error can be prevented by recruiting a larger sample size.

135
Q

When does a type 1 error occur?

The null hypothesis is REJECTED when it is true

A

A type I error occurs when the investigators conclude that there is a difference in a study when in reality there is none. Investigators usually set an arbitrary value such as 0.01 or 0.05.

This means that the investigators accept that there is a 1% or 5% chance that any difference detected is due to chance.

136
Q

Lead time bias

A

A lead-time bias is introduced in a study when a disease is detected an earlier stage and this gives the impression that the survival time from the detection point has increased. In reality, the increase in survival time is because the disease is detected earlier and the time of death remains unchanged.

137
Q

In the analysis stage of an experiment how can confounding variables be controlled for?

A

In the analysis stage of an experiment, confounding can be controlled for by stratification.

NOT RANDOMISATION

138
Q

What systems are in place in the NHS to try and prevent errors occurring?

A

 National Patient Safety Agency (NPSA) - 2001. coordination of reporting and learning from mistakes that affect patient safety.

 National Reporting And Learning System (NRLS) - 2004. National system for anonymous reporting of patient safety incidents, including near misses. All trusts now have a local system for reporting, linked to the national system. Also has a E- form for reporting incidents anonymously directly to the NPSA.

 Medicines and Healthcare - Products Regulatory Agency (MHRA) - Ensures medicines, healthcare products and medical equipment meet appropriate standards of safety, quality, performance and effectiveness and that they are used safely. Monitoring of medicines and acting on safety concerns. Responsible for adverse incident reporting system for medical devices.

139
Q

How to know if a hospital is safe?

A

Hospital mortality data

Data on other measures of safety:

  • Reports of never events and serious incidents
  • NHS safety thermometer
  • Patient safety dashboards

Monitoring and inspections by regulators

  • Care quality commission (CQC)
  • NHS improvement
140
Q

Effects of computer support on prescribing?

A 
 Reduced time to achieve therapeutic stabilisation
 Reduced risk of toxic drug level
 Reduced length of hospital stay
 Increased size of initial dose
 Increased serum drug concentration
 No change in adverse effects of drug
141
Q

Staph aureus infection

A

 Transmission - Contaminated food by skin/nasal flora
 Produces enterotoxins
 Incubation - 2-4 hours
 Symptoms - Rapid onset, projectile vomiting and diarrhoea

142
Q

Salmonella infection

A

 Transmission - Ingestion of contaminated food, faecal contaminations, person- person, infected animals
 Can cause enteric fever or enterocolitis
 Incubation period - is 12-72 hours
 Symptoms - Vomiting, diarrhoea, fever, headache, chills

143
Q

Cryptosporidium infection

A

 Transmission - Animal-human, person-person, contaminated water or land, associated with foreign travel
 Incubation - 2-5 days
 Symptoms - Watery or mucoid diarrhoea, severe illness in immunocompromised

144
Q

Escherichia coli infection

A

 Transmission - Contaminated food, person-person
 Incubation - 1-6 days
 Symptoms - Haemorrhagic colitis, 5% get haemolytic uraemic syndrome

145
Q

What is an outbreak?

A

Incident in which two or more people, thought to have a common exposure, experience a similar illness or proven infection

146
Q

What might outliers in an outbreak represent?

A 
 Baseline level of illness
 Outbreak source
 A case exposed earlier than the others
 An unrelated case
 A case exposed later than the others
 A case with a longer incubation period
147
Q

How can analytical epidemiological studies be useful to identify probably food source of outbreak?

A

 Compare food history of ill and well persons
 Point source outbreak - Cohort study
 Common source of outbreak - Case-control study

148
Q

Main dietary associated with cancer

A

 Oesophageal - Alcohol, obesity
 Stomach - Possible salted preserved foods
 Pancreas - Overweight, obesity
 Hepatic - Aflatoxin contamination
 Colorectal - Preserved and red meat, alcohol, body fat
 Breast - Alcohol, overweight
 Urologic - high calcium

149
Q

What are the different types of results?

A

 Therapy - Look at relative risk reduction, absolute risk reduction, odds ratio, number needed to treat, confidence intervals

 Diagnosis - Look at sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratios

 Prognosis - Look at how likely the outcomes are over time and how precise the prognostic estimates are (relative risk or odds ratios)

 Harm/aetiology - Look at relative risk, odds ratio, number needed to harm

150
Q

The National Service Framework on Children and Young People has made suggestions for the improvement of children’s health including accidents.

Give three key messages that the NSF suggests to improve child health.

A

Tackle health inequalities including poverty

Improving access to services/information

Focus on early intervention/Sure Start

Promote physical mental and emotional wellbeing

Promote healthy lifestyles

Setting standards

151
Q

Compare the importance of childhood accidents with other causes of child ill health and death.

A

Accidents are a major cause of death in children

They cause twice as many deaths in children as cancer and leukaemia

Cause 6 times as many childhood deaths as murder (homicide)

The incident rate of childhood accidents has not fallen in recent decades as quickly as, for example, diphtheria and pneumonia

152
Q

What are the arguments for and against age-based rationing being applied to micro-level resource allocation decisions?

A

 For - Age should be relevant because older people are less likely to respond to treatment and have a poorer prognosis in general due to increased complication risk

 Against - Age alone is not a good predictor of prognosis/complications hence need case-by-case decisions, decisions based on age may be hidden form of discrimination

153
Q

Which act protects discrimination based on age, race, sex, gender, disability, religion etc.?

A

Equality Act 2010

154
Q

What do clinical and economic evaluations investigate?

A

Clinical - efficacy and effectiveness

Economic - efficiency

155
Q

Advantages of systematic reviews over other research designs for answering clinical questions.

A

A systematic review is a rigorous summary of all the research evidence that relates to a specific question.(1 mark)

By bringing together all the relevant evidence disadvantages of single studies can be guarded against.(1 mark)

156
Q

Identify two potential weaknesses of the search strategy used by the authors of the review (for systematic review).

Explain why these features might bias the findings of the review

A
  • They have only looked at publications in English
  • They have only searched one database – e.g. Medline
  • Relevant publications might be published in non English language journals.
  • Not all relevant articles may be indexed in Medline.
  • A thorough search will reduce the risk that studies that might influence the results of the review will be missed
  • Trial reports that are translated for publication in English language journals tend to have bigger effect sizes (i.e. so English-language only searches tend to overstate the effect of an intervention).
157
Q

What are the different consumer protection agencies?

A
  • Care quality commission (CQC)
  • National Institute for Health and Clinical Excellence (NICE)
  • DoH and NHS England: oversight of cost and quality control
  • GMC: regulates medical schools and practitioners
  • Royal colleges: examine and certify practitioners
158
Q

National service framework?

A

 Set national standards and define service models for a service or care group

 Put in place programs to support implementation

 Establish performance measures against which progress within agreed timescales would be measured

159
Q

How can consumer protection be improved?

A

 Appraisal by peers

 Revalidation by the GMC

 Medical audit as a compulsory part of routine practice and annual job planning

 GP and consultant contracts - Increasing transparency in comparative performance
in relation to activity, costs, and patient reported outcomes

 Transparency and accountability

160
Q

General fertility rate

A

General fertility rate = number live births per 1000 women between ages 15-44

161
Q

Positive predictive value (FP)

A

Probability that those with positive result truly have the disease.

It is a measure of false positives.

Depends on population.

162
Q

Negative predictive value (FN)

A

Probability that those with a negative result truly are disease free.

It is a measure of false negatives.

Depends on population.

163
Q

Specificity (TN)

A

The probability of a negative, if the patient really is not ill

True negatives (TN)

TN / ( TN + FP)

true negatives / all truly disease-free

164
Q

Sensitivity (TP)

A

The probability of a positive, if the patient really is ill.

True positives (TP)

TP / (TP + FN)

true positives / all truly disease

165
Q

Summary of sensitivity, specificity, PPV, NPV.

A 
Sensitivity = TP
Specificity = TN
PPV = FP
NPV = FN
166
Q

Relative risk

A

One populations risk compared to another population.

The risk of developing disease for one population with an exposure compared with a population without the exposure?

E.g. smokers are 20 times more likely to contract lung cancer than non-smokers

E.g. women are 100 times more likely to get breast cancer than men.

167
Q

Absolute risk

A

One population’s risk in its own right.

AKA lifetime prevalence in that population.

E.g. women have a 11% risk of getting breast cancer.

168
Q

Principles of ethical research

A

Do good (or at least do no harm).

  • Equipose
  • Stop trial early if necessary
  • Individual vs population

Informed consent.

Protect anonymity and confidentiality.

Avoid deceptive practices.

Right to withdraw.

169
Q

What does high incidence to prevalence ratio mean?

A

High incidence to prevalence ratio means high death or cure rate

170
Q

Cancer

A 
Risk factors:
Smoking
Obesity/diet
Alcohol
Lower socioeconomic class

Specific risk factors:
Previous radiotherapy
Occupational

171
Q

Coronary artery disease

Highest cause of death in developed countries.

A 
Non-modifiable risk factors:
Male
Asian ethnicity
Age
Family history

Modifiable risk factors:
High blood pressure
Cholesterol
Diabetic control

172
Q

Lung cancer risk factors

A

SMOKING (RR 3, 90% of lung cancers)

Occupational (Asbestos, Dust diseases, Chromium, Arsenic, Radiation)

Age

Male > female (confounder = smoking)

173
Q

Tuberculosis

A

1/3 of the world’s population

20% have HIV

Urban areas

At-risk countries (south Asia, sub-Saharan Africa)

174
Q

Ethical principles

A

Autonomy: Patient’s right to self-rule of their body

Non-maleficence: Not doing harm

Beneficence: Doing good

Justice: Fair and equal access to healthcare

175
Q

Ethical theories

A

Deontology – people should adhere to their duties and obligations.
Consistent and does not vary.
Follows rules rigidly.

Utilitarianism: Greatest good for the greatest number.

Consequentialism: Consequences of actions are the determinant of the validity of an action.

Intentionalist: Intentions of actions are determinant of their validity.

176
Q

Duty of care

A

A moral or legal obligation to ensure the safety or well-being of others.

Maintain and improve safety and quality of care.

Raise and act on concerns about patient safety.

Use resources efficiently, to benefit the patient and the public.

177
Q

Negligence

A

A breach of the legal duty of care which results in damage.

Often passive, can be omission.

Failure to exercise the degree of care that a careful or prudent practitioner would have exercised under like circumstances.

Criminal negligence: Non-consensual treatment/Not acting in best interests

178
Q

Errors

A

Medical error: a mistake that could have been prevented
Can involve medicines, surgery, diagnosis, treatment or lab reports.

Human factors.

Near miss: an event that might have resulted in a hazard, but it did not because of timely intervention

179
Q

Capacity

A

Factors meaning a patient has capacity:

  • Understand the information relevant to the decision
  • Retain that information
  • Use or weigh up that information and come to a conclusion
  • Communicate that decision

May have capacity for some decisions but not others.

Adults have assumed capacity.

180
Q

Gillick competence

A

“A parent yields to the child’s right to make his own decisions when he reaches a sufficient understanding and intelligence to be capable of making up his own mind on the matter requiring decision”

Typically assessed in over 13s

Often can accept not deny treatment

181
Q

Fraser guidelines

A

For seeking contraception though <16.

The girl understands the advice

Cannot be persuaded to tell parents.

Likely to continue having sex anyway.

If contraception not received, health will suffer.

Best interests to give contraceptive advice.

Consultation should be kept confidential regardless.

Unless <13, refer to child protection.

182
Q

Current screening programmes

A

> Antenatal and newborn, routine, all newborns
Cervical cancer: 25-65, F
Breast cancer: 50-70, F
Bowel cancer: FOB at 60-74, endoscopy at 55
Abdominal aortic aneurysm: 65, M

183
Q

The Black Report

Reasons for inequalities in health.

A

Statistical artefact - Not genuine.

Natural or social selection - Those who are less well become poorer.

Materialist explanation - Exploitation of the lower socioeconomic classes.

Cultural/behavioural explanations - Eg. drinking.

184
Q

Prevention

A

Primary prevention:

  • Before the disease has occurred
  • E.g. Warnings on cigarette packets, vaccines, legislation, lifestyle campaigns

Secondary prevention:

  • Reduce the impact of the disease
  • E.g. Bike helmets, early detection and diagnosis though screening

Tertiary prevention:

  • Reduce the long term effects of the disease
  • E.g. Support groups, disease management
185
Q

Technical efficiency

A

The relationship between resources and health outcome.

Maximal possible improvement in outcome from a limited resource.

Lowest dose for greatest effect.

186
Q

Allocative efficiency

A

The efficiency in which healthcare resources are used to produce outcomes AS WELL AS the distribution among the community.

Maximal good for most people.

187
Q

Define guidelines

A

Guidelines: statements that include recommendations to optimise patient care that are informed on a systematic review of the evidence alongside expert opinion

188
Q

Define protocols

A

Protocol: a set of rules to be followed by healthcare providers for a specific situatio

189
Q

Types of bias

A

Selection bias: those included in a trial do not reflect a typical population, e.g. excluding those aged over 65 years from a study into ischaemic heart disease

Information bias: wrongly assigning trial participants incorrect diagnoses/ exposures

Reporting bias: cases with disease remember exposures better than those who are disease free

Interviewer bias: an interviewer may ask patients with disease more questions about exposures than those who are disease free

Loss to follow-up: if a significant proportion of trial participants drop out as time progresses, then the final data cannot be reliably interpreted

Lead time bias: earlier diagnosis of a condition results in an apparently longer survival time (see Fig. 8.1)

Publication bias: trials with positive results are much more likely to be published

190
Q

Power

A

Probability of rejecting the null hypothesis when it is false

191
Q

Hazard ratio

A

Similar to relative risk but used when risk is not constant

192
Q

Cohort studies

A

Cohort studies are usually but not exclusively prospective, the opposite is true for case-control studies. The following notes relate cohort to case-control studies:

  • Outcome is measured after exposure
  • Yields true incidence rates and relative risks
  • May uncover unanticipated associations with outcome
  • Best for common outcomes
  • Expensive
  • Requires large numbers
  • Takes a long time to complete
  • Prone to attrition bias (compensate by using person-time methods)
  • Prone to the bias of change in methods over time
  • Related methods are risk (prospective), relative risk meta-analysis, risk difference meta-analysis and proportions
193
Q

Case control studies

A

Case-Control studies are usually but not exclusively retrospective, the opposite is true for cohort studies. The following notes relate case-control to cohort studies:

  • Outcome is measured before exposure
  • Controls are selected on the basis of not having the outcome
  • Good for rare outcomes
  • Relatively inexpensive
  • Smaller numbers required
  • Quicker to complete
  • Prone to selection bias
  • Prone to recall/retrospective bias
  • Related methods are risk (retrospective), chi-square 2 by 2 test, Fisher’s exact test, exact confidence interval for odds ratio, odds ratio meta-analysis and conditional logistic regression.
194
Q

Bias

A

Bias is a systematic error that leads to an incorrect estimate of effect or association. Many factors can bias the results of a study such that they cancel out, reduce or amplify a real effect you are trying to describe.

Epidemiology categorises types of bias, examples are:

  • Selection bias - e.g. study of car ownership in central London is not representative of the UK.
  • Observation bias (recall and information) - e.g. on questioning, healthy people are more likely to under report their alcohol intake than people with a disease.
  • Observation bias (interviewer) - e.g. different interviewer styles might provoke different responses to the same question.
  • Observation bias (misclassification) - tends to dilute an effect
  • Losses to follow up - e.g. ill people may not feel able to continue with a study whereas health people tend to complete it.

Some strategies to combat bias:

  • Multiple control groups
  • Standardised observations (e.g. single, double, or triple blinding)
  • Corroboration of multiple information sources
  • Intention to treat analysis: done to avoid the effects of crossover and dropout, which may break the random assignment to the treatment groups in a study.
195
Q

Confounding

A

In epidemiology a confounder is:

  • Not part of the real association between exposure and disease
  • Predicts disease
  • Unequally distributed between exposure groups

A researcher can only control a study or analysis for confounders that are:

  • Known
  • Measurable

Strategies to reduce confounding:
- Randomization (aim is random distribution of confounders between study groups)
- Restriction (restrict entry to study of individuals with confounding factors - risks bias in itself)
- Matching (of individuals or groups, aim for equal distribution of confounders)
- Stratification (confounders are distributed evenly within each stratum)
- Adjustment (usually distorted by choice of standard)
multivariate analysis (only works if you can identify and measure the confounders)

196
Q

Calculate odds of being a case among the exposed

a - exposed case
b - exposed control
c - unexposed case
d - unexposed control

Calculate odds of being a case among the unexposed.

Calculate the odds ratio of exposed vs non-exposed cases.

A

Odds of being case among all exposed = a/b

Odds of being case among all unexposed = c/d

Odds ratio: (a/b)/(c/d) = ad/cb (mathematical simplification)

197
Q

What would an odds ratio (OR) of 0.6, 1.0 and 3.2 indicate?

A

OR of 0.6 indicates that exposure is negatively associated with disease (is a protective factor).

OR of 1.0 means that exposure is not related to disease.

OR of 3.2 would indicate that exposure is positively associated with disease.

198
Q
  1. When is it NOT appropriate to use the odds ratio to approximate the relative risk?
    a. When the controls’ exposure history is representative of all subject without disease
    b. When the case selection is representative of all subjects with disease (e.g. unbiased incident cases)
    c. When the study disease occurs frequently
    d. When the study outcome is rare
A

c. When the study disease occurs frequently

199
Q

Risk difference

A

Synonyms: absolute risk reduction, attributable risk

Risk difference: the difference in the probability of an event occurring over a given time between two groups

200
Q

What is number needed to?

A

A communication tool for the absolute difference in risk observed in different situations.

201
Q

NNt calculation

A

NNt = 1 / |risk difference|

risk difference = ARR etc so 1/ARR is also correct

202
Q

What is the inverse care law?

A

Inverse care law: the availability of good medical care tends to vary inversely with the need of the population served

203
Q

CAT RCT: How precise are results?

A

Confidence intervals

P-values

204
Q

CAT Cohort: Was the cohort recruited in appropriate way?

A

Selection bias

Is sample representative of general population?

205
Q

CAT Cohort: Was exposure accurately measured to minimise bias?

A

Were subjects classified into exposure groups using same/appropriate procedure?

Do measurements reflect what you want them to?

  • Inappropriate measurement could cause type 1 or 2 statistical errors
206
Q

CAT Cohort: Was outcome accurately measured to minimise bias?

A

Reliable system established to ensure detection of all cases? (were measurement methods similar in different groups)

Blinding of subjects/observers

  • Was outcome established blind to exposure
  • Assess confounding variables and other differences in cohorts
207
Q

CAT Cohort: Have authors identified important confounding factors?

A

Have they taken confounders in account in design or analysis?

Degree to which confounding variable is present.

  • Define confounder: distortion of association between outcome and exposure by a third factor which has an association with both exposure and outcome.
  • Confounder can lead to biased association between exposure and outcome.
208
Q

CAT Cohort: Was follow up of subjects long enough/complete?

A

Not long enough for exposures affect on outcome to manifest and be detected.

Completeness important because those lost may have different outcomes than those who continue the study (intention to treat analysis)

  • Incomplete follow-up allows for selection bias.
  • May reduce power of the study
  • A bias towards the null AND outcome exposure associations may have been underestimated.
209
Q

CAT Cohort: Was the cohort recruited in appropriate way?

A

Importance of cohort being representative of population.

210
Q

CAT Cohort: What are the results of the study?

A

Are they statistically significant.

211
Q

CAT Cohort: Application?

A

Description of study cohort to allow comparison with local population.

  • Assess if study cohort similar to local population
  • Any treatment differences etc?
212
Q

CAT Cohort: Appropriate study?

A

RCT are gold standard for assessing cause and effect.

However it is not ethical to allocate patients to certain exposure that may be harmful.

Not practical - patients may choose to change behaviour and this cannot be controlled.

213
Q

CAT Case-control: Were the cases recruited in acceptable way?

A

Selection bias - may compromise validity

Are cases defined precisely?

  • Representative of defined population?
  • Established reliable system of selecting cases?
  • Is time frame of study relevant to the disease/exposure?
  • Sufficient number of participants (power)?
  • Anything special about cases?
214
Q

CAT Case-control: Was the controls selected in an appropriate way?

A
  • Controls representative of defined population? - geographically/temporally
  • Anything special about controls?
  • Are they matched, population based or randomly selected?
  • Sufficient number?
215
Q

CAT Case-control: Was exposure accurately measured to minimise bias?

A

Measurement, recall or classification bias?

  • Exposure clearly defined and accurately measured?
  • Subjective/objective measurements?
  • Do measures truly reflect this (validated)?
  • Were methods similar in cases and controls?
  • Did the study incorporate blinding where feasible?
216
Q

Benefits of systematic reviews

A

Include all evidence to answer question.

Increase total sample size which improves power which improves certainty and precision.

217
Q

What should be included in the search strategy of systematic reviews?

A
  • Hand-searching
  • Conference proceedings
  • Contacting authors
  • Papers in non-english
  • Including unpublished studies

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