Block 10 H + S

Question 1

What is sensitivity?

Answer 1

-True positives

- Measures the proportion of positives that are correctly identified

Question 2

What is the equation for sensitivity?

Answer 2

Sensitivity= true positives/ true positives + false negatives

Question 3

What is specificity?

Answer 3

-True negatives

- Measures the proportion of negatives that are correctly identified

Question 4

What is the equation for specificity?

Answer 4

Specificity= true negatives/ true negatives + false positives

Question 5

What is a diagnostic test?

Answer 5

Any kind of medical test performed to aid the diagnosis or detection of disease

Question 6

What are the uses of diagnostic tests?

Answer 6

-Diagnosis
- Monitoring
- Screening
 -Prognosis

Question 7

How is sensitivity and specificity important in informing diagnosis?

Answer 7

The importance of a diagnostic accuracy in testing is directly proportional to the tests potential to cause patient consequences and harm.

Question 8

What does true positive mean?

Answer 8

Test indicates disease when there is disease

Question 9

What does true negative mean?

Answer 9

Test indicates no disease when there is no disease

Question 10

What does false positive mean?

Answer 10

Test indicates disease when there is no disease

Question 11

What does false negative mean?

Answer 11

Test indicates no disease when there is disease

Question 12

What is positive predictive value?

Answer 12

The probability that subjects with a positive screening test truly have the disease

Question 13

What is negative predictive value?

Answer 13

The probability that subjects with a negative screening test truly don’t have the disease

Question 14

What is the likelihood ratio?

Answer 14

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

Question 15

What is screening?

Answer 15

Systematic application of a test or inquiry, to identify individuals at sufficient risk of a specific disorder to warrant further investigation or direct preventive action, amongst persons who have not sought medical attention on account of symptoms of that disorder

Question 16

What is the purpose of screening?

Answer 16

-Opportunities for primary prevention are limited
- Opportunities for treatment are limited
- Screening gives potential for early and more effective treatment

Question 17

What is commonly screened for?

Answer 17

-Cancer - Colorectal cancer, Breast cancer, Cervical cancer
- PPD test - Tuberculosis
- Prenatal tests - Foetal abnormalities
- Newborn bloodspot test - PKU, cystic fibrosis etc
- Ophthalamoscopy or digital photography and image grading - Diabetic retinopathy -Ultrasound scan - Abdominal aortic aneurysm
- Screening for metabolic syndrome
- Screening for potential hearing loss in newborns

Question 18

What are the limitations of screening?

Answer 18

-Cost and use of medical resources on a majority of people who do not need treatment
- Adverse effects of screening procedure - Stress, anxiety, discomfort, radiation exposure
 -Stress and anxiety caused by a false positive result
 -Unnecessary investigation and treatment of false positive results
 -Stress and anxiety caused by prolonging knowledge of an illness without any
improvement in outcome
 -A false sense of security caused by false negatives, which may delay final diagnosis

Question 19

What are the pros and cons of good screening?

Answer 19

-Pros - Early detection of disease means the risk of death or illness can be reduced for some people
- Cons - Some people get tests, diagnosis and treatment with no benefit. Some people get ill or die despite a negative screening test

Question 20

What areas should be evaluated when deciding what should be screened for?

Answer 20

-Condition - Important? epidemiology, natural history of condition, detectable risk factor, latent period, cost-effective
- Test - Simple, safe, precise, validated, cut-off agreed, acceptable
- Treatment - Effective evidence based treatment
- Programme - RCT evidence of reduction in mortality or morbidity, benefit outweight
harm, opportunity cost, quality assurance

Question 21

What is sojourn time?

Answer 21

-The duration of a disease before clinical symptoms become apparent but during which it is detectable by a screening test.
- Its clinical relevance is that it represents the duration of the temporal window of opportunity for early detection.
- Length of sojourn time short - Rapidly progressing disease, poorer prognosis
- Length of sojourn time long - Better prognosis

Question 22

What is length bias?

Answer 22

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

Question 23

What are the consequences of length bias?

Answer 23

-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

Question 24

What is lead time bias?

Answer 24

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

Question 25

What are the consequences of lead time bias?

Answer 25

-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

Question 26

What is overdiagnosis bias?

Answer 26

• 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

Question 27

What is PSA testing and what causes it to be raised?

Answer 27

-Prostate-specific antigen (PSA) - protein produced by cells of the prostate gland
- Elevated in - Prostate cancer, BPH, prostatis, UTI

Question 28

What are some advantages of PSA testing?

Answer 28

-Can help detect tumours with no symptoms
- Allows estimation of prostate size and stage
 -Helps doctor predict response to treatment
 -Can be used to monitor men who are at increased risk

Question 29

What are some disadvantages of PSA screening?

Answer 29

-Early detection may not reduce the chance of dying from prostate cancer
-Overdiagnosis -> overtreatment
- May give false-positive - Other conditions can increase PSA, not specific enough
- May give false-negative

Question 30

What are some of the impacts that incontinence might have on a patient?

Answer 30

-Distress
- Embarrassment
- Inconvenience
- Threat to self esteem
- Loss of personal control
 -Desire for normalisation
- loss of interest in sex
 -Difficulty sleeping (especially with nocturia)

Question 31

What impact might chronic dialysis have on a patient

Answer 31

-Regular hospital admissions
- Restriction of leisure time
- May have to give up job
- Increased dependence on dialysis
- Uncertainness about the future
- Fatigue
- Limitation of liquids and foods
 -Disrupts family and friend relationships
- Depression
- Lower self-esteem

Question 32

What is opportunity cost?

Answer 32

-The loss of other alternatives when one alternative is chosen.
- The amount of money that is alienated by choosing to use it for one project rather
than another

Question 33

What is distributive justice?

Answer 33

How we distribute resources that are finite in a fair way.

Question 34

How can you decide ways to distribute healthcare?

Answer 34

-QALY calculation
- Waiting list
- Likelihood of complying with treatment
- Lifestyle choices of patient
- Ability to pay

Question 35

What is confidentiality?

Answer 35

Pledge of agreement to not divulge or disclose information about patients to others

Question 36

Why is it important to maintain confidentiality

Answer 36

-Improves trust between patient and doctor
 -Respects autonomy
 -Prevents patient harm
 -Virtuous
- Human rights act
- GMC requirement

Question 37

When can confidentiality be breached?

Answer 37

-Statute (law)
- Consent by patient
- Public best interest

Question 38

Name some laws that oblige doctors to disclose information?

Answer 38

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