Statistics

Question 1

What is sensitivity?

Answer 1

Sensitivity

Proportion of people with the disease who have a positive test.

Question 2

What is specificity?

Answer 2

Proportion of people without the disease who have a negative test.

Question 3

How does prevalence affect sensitivity and specificity of a test?

Answer 3

It doesn’t.

Unlike sensitivity and specificity, PPV and NPV values vary with the prevalence of a condition within a population.

Question 4

What is screening?

Answer 4

Screening is a process of identifying apparently healthy people who may be at increased risk of a disease or condition.

They can then be offered information, further tests and appropriate treatment to reduce their risk and/or any complications arising from the disease or condition.

Question 5

What are 3 main criteria for screening?

Answer 5

The condition

The condition sought should be an important health problem. Its natural history,- understood, and it should have a recognisable latent or early symptomatic stage.

The test

There should be a simple, safe, precise and validated screening test that is acceptable to the population.

The treatment

There should be an effective treatment or intervention for patients, with evidence that early treatment leads to better outcomes than late treatment.

Question 6

What is the Department of Health target for screening pregnant women for HIV?

Answer 6

The Department of Health target of screening 80% of pregnant women is estimated to reduce the risk of vertical transmission to infants by 80%

Question 7

What are NSC approved screening programmes in the UK?

Answer 7

HIV/Hep B and syphilis in pregnancy

Cervical screening

Question 8

What are non NSC approved screening programmes in UK?

Answer 8

chlamydia, gonorrhoea, HIV, syphilis, hep B- in GU setting

Question 9

What are 2 main approaches for delivering screening programmes?

Answer 9

Register based

Opportunistic

Question 10

How to put your 2 x 2 together for sensitivity/specificity

Answer 10

DISEASE at top

Test results down side

Question 11

What is a phase 1 clinical trial?

Answer 11

In a phase 1 clinical trial, the tolerability and SAFETY of the new drug is studied, usually in a small number of healthy volunteers.

Question 12

What is a phase 2 clinical trial?

Answer 12

Phase 2 is aimed at determining the drug’s efficacy and optimal dosing regimen.
ie does the treatment work?

Question 13

What are phase 3 clinical trials?

Answer 13

Phase III clinical trials: Is it better than what’s already available?

Question 14

What are phase 4 clinical trials?

Answer 14

Phase IV clinical trials: What else do we need to know?

Question 15

Strength of recommendation- Level of evidence 1

Answer 15

Strong recommendation

Question 16

Grading of evidence level A

Answer 16

A. High quality evidence
Benefits clearly outweigh the risk and burdens or vice versa

Consistent evidence from well performed randomised controlled trials or overwhelming evidence of some other form.

Question 17

Grading of evidence level C

Answer 17

C. Low-quality evidence
Benefits appear to outweigh the risk and burdens or vice versa
Evidence from observational studies, unsystematic clinical experience or from RCTs with serious flaws. Any estimate of effect is uncertain.

Question 18

Grading of evidence level B

Answer 18

Moderate quality evidence
Benefits clearly outweigh risk and burdens or vice versa
Evidence from randomised controlled trials with moderate limitatons (inconsistent results, methodological flaws, indirect or imprecise) or very strong evidence from some other research design.

Further research may impact on our confidence in the estimate of benefit or risk.

Question 19

Strength of recommendation- Level of evidence 2

Answer 19

2. Weak recommendation

Question 20

Grading of evidence level D

Answer 20

D. Very low quality evidence

Benefits appear to outweigh the risk and burdens or vice versa Evidence limited to case studies