3- Screening

Question 1

Outline criteria that should be met before implementing a public screening program

Answer 1

1. Condition should be an IMPORTANT health problem
   
   • causes death or disability
   • large no affected, common
   • causes bad
2. There should be an ACCEPTED TREATMENT for pts with recognised disease, treatment should be better at an earlier stage
3. FACILITIES for diagnosis and treatment should be available
4. Should be a recognised EARLY or LATENT phase
5. There should be a SUITABLE TEST or exam- sensitive, specific
6. Test should be ACCEPTABLE to patients- not too harmful
7. Natural history of condition should be adequately UNDERSTOOD
8. CUT OFF for confirmatory test- agreed upon policy on who is a pt
9. COST EFFICACY- diagnosis and treatment
10. Case finding should be a CONTINUING process, not a once and for all project.

Question 2

Explain lead time bias

Answer 2

New screening detects disease earlier, doesn’t affect disease outcome- false impression of longer survival.

Question 3

Explain lead time

Answer 3

Time between detectable by screening and symptomatically

Question 4

Explain length time bias

Answer 4

Chronic and acute disease
Most people with chronic as slow disease progress and people are in detectable stage longer
Screen more often for disease with slower progress- screened disease have better prognosis already

Question 5

4 benefits of screening tests

Answer 5

Early diagnosis
Better prognosis
Prevent disease
Cheaper to treat early

Question 6

7 disadvantages of screening test

Answer 6

Expensive
Anxiety
Test causes harm directly- eg CT are ionising
Can’t detect all disease
False -ve pt may delay presenting symptomatic disease if falsely reassured
False +ves
Over diagnosis