Secondary prevention

Question 1

What is secondary prevention?

Answer 1

To reduce the impact of disease or injury, that has already occurred, through early detection and treatment.

Question 2

What is the aim of secondary prevention?

Answer 2

To improve prognosis

Prevent or slow progression

Question 3

What methods does secondary prevention use?

Answer 3

Screening, diet, education and exercise

Question 4

What is screening?

Answer 4

A process of identifying apparently healthy, asymptomatic people who may be at an increased risk of a disease or condition. Early detection of disease, precursor or genetic susceptibility.

Question 5

What happens if screening identifies a risk?

Answer 5

If identified, further test and treatment follows to reduce the risk of complications arising from the condition.

Question 6

What is a screening test compared to?

Answer 6

A gold standard diagnostic test that confirms result of screening, producing true and false results, to determine the screening sensitivity and specificity.

Question 7

What is sensitivity?

Answer 7

How good the screening method is at identifying those with the disease to reduce the number of FALSE -VEs.

Question 8

What is the calculation for sensitivity?

Answer 8

True +ve / (True +ve + False -ve)
How many true +ves/ cases it can detect
High % shows sensitivity

Question 9

What is specificity?

Answer 9

How good the screening method is at excluding those without the disease to reduce the number of FALSE +VEs.

Question 10

What is the calculation for sensitivity?

Answer 10

True -ve / (True -ve + False +ve)
How many true -ve it can detect
High % shows specificity to the disease

Question 11

How can false results be reduced?

Answer 11

By having a strict criteria for the screening test.

Question 12

What is the purpose of predicted values?

Answer 12

To show how likely it is that a results is correct.

Question 13

What is the PPV and what does it show?

Answer 13

PPV = True +ve / (True +ve + False +ve)
A high PPV shows less false +ve results
A low PPV shows high false +ve results

Question 14

What is the NPV and what does it show?

Answer 14

NPV = True -ve / (True -ve + False -ve)
Shows the chance of not having / being a true -ve.
NPV is usually high

Question 15

What affects the NPV?

Answer 15

Prevalence - If prevalence of a disease is >90% of a population, NPV will fall as will see more True +ves than -ves.

Question 16

What is the calculation for prevalence?

Answer 16

True +ve + False -ve / All tested

Question 17

What is a screening programme?

Answer 17

Screening test plus options available for the Pt when the risk is identified.

Question 18

What are the risks of screening for each result arm?

Answer 18

True +ve leads to labelling, identifying a disease which has no treatment.
False +ve would cause unnecessary anxiety, fear and cost
False -ve creates false reassurance and causes a delay in intervention
True -ve undergone invasive, time consuming and costly tests.

Question 19

When will screening for a condition be allowed?

Answer 19

If the condition has an understood timeline with an identified pre-clinical phase in which it is detectable.
There is treatment available that will alter the outcome and has RCT evidence.
Benefits must outweigh the risks.
The disease must be significant, of high prevalence and fatal within a population.
At a reasonable cost.
Have high specificity and sensitivity.

Question 20

What screening tests are available in UK?

Answer 20

Breast, cervical and colon

Question 21

What screening tests are available that are non-NSC?

Answer 21

Prostate, chlamydia and vascular risk

Question 22

What is volunteer bias?

Answer 22

Pts who volunteer and attend screening are more likely to be health conscious and have a healthier lifestyle than those that don’t, lowering their risk of having the disease.

Question 23

What is lead time bias?

Answer 23

Time between early detection and clinical presentation will appear to be increased and survival time increased, if Pts are detected early, compared to those not screened.

Question 24

What is length time bias?

Answer 24

Less aggressive diseases have a longer pre-clinical phase and so are more likely to be detected by screening and have a better prognosis.