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Epidemiology and Biostatistics Flashcards

1
Q

What is a RCT?

A

Randomised Controlled Trials
Intervention study
Choice treatment/intervention allocated randomly to new vs current/placebo

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2
Q

Why randomise RCTs?

4 reasons

A

Patients’ characteristics x affect which treatment received
Unbiased + treatment groups balanced
Any differences in outcome attributed to treatment received
Fair test of efficacy

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3
Q

What are case controlled studies?

A

Observational study, x intervention
Observe natural state (real world)
Investigate causes/factors associated mit disease/condition
Select group with + without disease - case + controls

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4
Q

What are 2 limitations of case controlled studies?

A

Choice of control group can affect comparison

Data reported by subjects/records - retrospective, may be incomplete/inaccurate/biased

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5
Q

What are cohort studies?

A

Observational, x intervational (natural state)
Investigate causes/factors associated mit disease/condition
Selects group healthy individuals
Follow-up to monitor disease state + possible risk factors

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6
Q

What are limitations of cohort studies?

A

Need big no to get enough mit disease
Oft need long follow-up
Need keep in touch mit participants
Expensive

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7
Q

What are cross sectional studies?

A

Observational, natural state

Collect data for each subject at 1 point in time only

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8
Q

What are cross sectional studies useful for?

A

Measuring prevalence of disease/condition

Surveys of attitudes/views/behaviours

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9
Q

Why is it necessary to summarise data?

A

Monitor data quality
Check for invalid/missing entries
Describe characteristics of participants in a study
Before doing complex analysis

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10
Q

What are the 2 types of quantitative data?

A

Continuous e.g. weight/height

Discrete e.g. no of children

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11
Q

What are the types of categorical data?

A

2 categories - Dichotomous/binary e.g. dead/alive, male/female
>2 categories: ordered/unordered (ordinal/nominal)

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12
Q

How to calculate incidence rate?

A

(Total no of new cases of a specific disease/total pop at risk during same time period) x 100^n

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13
Q

How to calculate prevalence rate?

A

(All new pre existing cases of specific disease during given time period/total pop during same period) x 10^n

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14
Q

What is a confidence interval?

A

Range within population value likely to be

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15
Q

What is a sampling error?

A

When diff samples give diff estimates

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16
Q

How to calculate standard error?

A

S.D/(square root of N)

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17
Q

Where is true/pop mean supposed to lie in relation to sample mean?

A

Sample mean +/- 1.96 SE in 95% of calc

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18
Q

What are the assumptions in calculating CI?

A

Normal data/large sample - at least 60
Sample chosen at random from pop
Observations independent from each other

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19
Q

What are 4 assumptions in population proportion?

A

Sample chosen at random from pop
Observations independent
Proportion mit characteristic x close to 0/1
np and n(1-p) greater than 5 (large sample)

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20
Q

Calculate proportion SE?

A

square root p(1-p)/n

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21
Q

Definition of p value?

A

P value probability of obtaining sample data as extreme/mehr extreme than that observed if null hypo true

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22
Q

What is clinical significance?

A

Diff observed is large enough to be clinically meaningful

Clinical judgement, x statistical

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23
Q

How often is a population census carried out?

A

Erry 10 years

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24
Q

What are enumeration districts?

A

Small area of 200 households

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25
How often are population estimates produced and by what method?
Annually | Cohort component method
26
How to calculate population estimate?
Previous mid-year resident pop Add age on by 1 year Add births during year + Remove deaths during year Allow for migration
27
What problem can occur with GP populations?
List inflation - registered pop greater than resident pop e.g. people move but x notify GP people who die X have records removed quickly
28
How often are population projections produced and who does them?
Erry 2 years | GAD - Government Actuary Department
29
What are the assumptions of population projections?
Mortality Fertility Migration Base pop (2000 estimates)
30
What are the indices of multiple deprivation?
``` Income deprivation Employment deprivation Health deprivation + Disability Education, Skills + Training deprivation Barriers to housing + services Living environment deprivation Crime ```
31
How often are the IMDs revised?
Erry 5 years
32
What are the 2 parts of a death certificate?
1st prt - Disease/condition directly related to death | 2nd prt - Other conditions x directly related
33
What prt of death certificate is classed as cause of death?
Lowermost disease/condition listed in 1st prt
34
How many parts in international classification of disease?
22 groups
35
What are the 3 classes of genetic traits?
Monogenic Oligogenic - influenced by few genes Polygenic
36
What is Bradford Hill criteria and how many criteria are there?
Minimal conditions necessary to provide adequate evidence of a causal relationship between an incidence + outcome 9
37
What are some advantages of case controlled studies?
Inexpensive + Quick Good for rare outcomes + multiple risk factors Can look at risk factors in detail
38
What are some disadvantages of case controlled studies?
X efficient study rare experiences Uncertainty of exposure-disease time relationship Inability provide direct estimate of risk Subject to biases ( recall + selection bias)
39
What are 4 features of case controlled studies?
Outcome 1st Retrospective Observational X follow up
40
What is misclassification and the types?
Measurement error leads to assigning wrong exposure/outcome category Non-differential - random error, unrelated to exposure/outcome status, weakens measure association, x bias Differential - systematic error, measure of association distorted in any direction
41
Definition of: a) Prevalence ratio? b) Odds ratio? c) Odds?
a) Prevalence of disease in exposed/prevalence disease in unexposed b) Ratio of prevalence odds in exposed to prevalence odds in unexposed c) Odds that diseased person exposed/unexposed
42
What are 4 pros of cross sectional studies?
Quick + easy to conducted Data collected once Measure prevalence for all factors Multiple outcomes + exposures
43
What are 5 cons of cross sectional studies?
``` Difficult determine time order Unsuitable study rare disease Difficult interpret Susceptible to bias Unable measure incidence ```
44
What is a cross sectional study?
Exposure status + disease status of an individual measured at 1 point time
45
What is a cohort study?
Groups of peeps share common experiences/conditions + are followed up to determine incidence of specific disease
46
What are the 3 types of cohort studies?
Retrospective Prospective Ambidirectional
47
How to calculate risk?
``` Risk = n/N n = new cases N = pop initially at risk ```
48
How to calculate rate?
``` Rate = n/Y Y = total person years at risk ```
49
What is the difference between incidence rate and incidence proportion?
Incidence rate - no of new cases in a given time period Incidence proportion - proportion of initially disease-free pop that develops disease/becomes injured/dies during given time period
50
Definition of equipoise?
X existing evidence that intervention/drug being tested will be superior to existing treatment/effective at all
51
Why is concept of equipoise used in RCTs?
RCT is justified if this concept exists
52
What are 4 basic RCT design questions?
Pop of interest? Intervention? Comparison? Outcome of intervention assessed?
53
How to calculate absolute risk reduction (ARR)?
(Risk in control) - (Risk in intervention)
54
How to calculate relative risk reduction (RRR)?
[(Risk in control) - (Risk in intervention)]/Risk in control
55
What does NNT stand for and calculation?
No needed to treat - no patients have receive treatment of interest in order prevent adverse events in 1 patient
56
What is the intention to treat analysis?
All individuals who were randomised should be inc in analysis Analysed according to allocated treatment + x treatment received Avoids bias from drop-outs, loss to follow-up + non-compliance
57
What is a meta analysis?
Statistical technique for combining findings from independent studies Precise estimate of treatment effect
58
What is a meta analysis validity dependant on?
Quality of systematic review on which it's based Coverage of all relevant studies Use of appropriate methods, taking care of heterogeneity
59
What is the protocol?
Document that describes how study will be conducted
60
What is study heterogeneity?
Studies whose results being combined in meta-analysis should all be undertaken same way + to same experimental protocols Term indicates that ideal X fully met
61
What is the fixed effect model?
Assumes common effect + within study only
62
What is the random effects model?
Underlying effects allowed to vary between studies
63
What is publication bias?
What research likely to be published among what's available to publish
64
What is screening?
Actively identifying disease/pre-disease + in apparently healthy individuals who may benefit from early treatment
65
What is population screening?
Entire population at risk is called to be screened
66
What is lead time?
Interval between time of detection of disease by screening + time at which disease would have been diagnosed
67
What are 3 biases associated with screening?
Length-biased sampling - rapidly progress disease prompt consultation compared to slow progression Selection bias Overdiagnosis bias - some lesion identify as disease due to screening but x present clinically before
68
3 pros of screening?
Improved prognosis for true +ves Less radical treatment required Resource savings
69
3 cons of screening?
Overtreatment of borderline abnormalities False reassurance of false -ve Hazard of screening test to all recipients
70
What is a diagnostic test?
Aids diagnosis/detection of disease
71
How to calculate sensitivity true +ve rate?
No of diseased individuals +ve to test/ total no of diseased individuals
72
How to calculate specificity true -ve rate?
No of disease-free patients -ve to test/total no of disease-free individuals
73
How to calculate positive/negative predictive value? (PPV/NPV)
No of diseased +ve to test/total no of individuals +ve to test No disease free patients -ve to test / total no individuals -ve to test
74
What is primary prevention?
Reducing risk of a disease/injury occurring in 1st place
75
What is secondary prevention?
Reducing risk of a disease/injury worsening/recurring
76
What is tertiary prevention?
Reducing risk of a disease/injury -vely impacting on a | person’s quality of life/ability to function
77
Benefits of individual approach to prevention?
Targeted only at higher-risk individuals 1-2, individually tailored, intensive Subject motivated; health professional trusted
78
Cons of individual approach to prevention?
Fewer people helped More labour-intensive Requires trained staff
79
Benefits of population approach to prevention?
Mass media, large no peeps Tackles all levels of risk Economies of scale Reduce pop average for risk factor(s) in question
80
Cons of population approach to prevention?
Generalised messages Tendency for public to distrust media Smaller individual health gains Only appropriate for common diseases
81
What are the 5 models of health promotion?
``` Medical Behavioural Empowerment Social Change Environmental ```

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