Clinical Prevention I: Screening Programs

Question 1

1. Define primary prevention, secondary, and tertiary:

Answer 1

Primary: preventing disease before it occurs (treating risk factors)
Secondary: think SCREENING and diagnosing the disease early, before it causes clinical symptoms
Tertiary: prevent complications of (and mortality from) diagnosed, clinical disease

Question 2

2. Define screening:

Answer 2

apply DIAGNOSTIC test to perfectly healthy patient to CATCH A DISEASE IN EARLY ASYMP STAGE

Question 3

3. Screening starts with ____; give some examples of this

Answer 3

diagnosis;
history questions (domestic violence), PE findings (bruits in carotids and abdomen), lab tests (invasive test)

Question 4

4. Results of screening trigger

Answer 4

prevention interventions

Question 5

5. For treatment as a screening test characteristic think; for population oriented prevention think

Answer 5

NPV;

PPV

Question 6

6. Screening test characteristics can depend on

Answer 6

invasiveness of test, cost of test, seriousness of disease, values of patients/community

Question 7

7. What do screening programs encompass? What do they want to find?

Answer 7

Test, confirmatory tests, treatment and follow-up for a disease;
EARLY, ASYMPTOMATIC disease and treat it to reduce morbidity and mortality later on

Question 8

8. What is the _____ criteria for screening programs?

Answer 8

FRAME;

1. disease is important
2. Test is accurate
3. Disease has early, asymp phase
4. Treatment exists
5. Treatment effective
6. Treating EARLY reduces morbidity and mortality

Question 9

9. An RCT

Answer 9

is the best evaluation of whether a screening program works (ie whether or not we should screen)

Question 10

10. List order on Screening and Prevention slide and where does screening test/treatment come in?

Answer 10

Pathological Onset, then disease symptoms, then DEATH: screening test and treatment ideally should come in before pathological onset and disease symptoms

Question 11

11. Primary prevention occurs during _____ phase, secondary and tertiary during which phases?

Answer 11

normal; preclinical; clinical!!

Question 12

12. Lead-time bias is

Answer 12

finding that someone has the disease (preclinical phase) through screening and diagnosis but could die at same time as someone who wasn’t screened and diagnosed early!!
Screening FALSELY appears to EXTEND LIFE

Question 13

13. Length time bias is; solution?

Answer 13

tends to overrepresent less aggressive disease (shorter lines indicate more aggressive and you might not catch these patients; instead, depending on your screening intervals, you might only catch less aggressive disease);
try to catch more aggressive disease somehow or screen more often!!

Question 14

14. Selection bias is

Answer 14

testing a screening test in those who agree to a screening test and comparing it to a population that did not get the test (would get more healthy people in volunteer group than non-volunteer group, affecting your INTERNAL VALIDITY; or worried-well people related to people with breast cancer, that could affect EXTERNAL VALIDITY)

Question 15

15. Overdiagnosis bias is

Answer 15

researchers evaluating a screening program and might be overzealous in diagnosing the disease and FALSELY concluding that the program is effective; THINK DCIS or DIABETES!!;

Think of that graph where you have 1000 people with clinical lung cancer and you have a certain 10-year survival rate, vs people with pseudodisease and survival rate being inflated!!!

Question 16

16. Referral bias is

Answer 16

if screening programs are evaluated in TERTIARY care offices: by default, your prevalence/pre-test prob will be HIGHER!! (this could differ from primary care office test-wise)

Question 17

Proper screening program evaluation would be

Answer 17

RCT of screening vs. no screening with long follow-up and appropriate interval of screening and selection of patients