Criteria for screening

1. CRITERIA FOR SCREENING

2. Successful Screening
Criteria for test
Criteria for disease

3. • CRITERIA FOR DISEASE:
- Should be an important health problem (High Prevalence).
- Should have an early asymptomatic stage.
- Natural history should be understood.
- Test should be present to diagnose the disease before sign & symptoms.
- Facilities for confirmation of diagnosis should be available.
- Effective treatment should be present.
- Agreed on policy on whom to treat should be present.
- Good evidence the it reduce mortality and morbidity should be present.
- Expected benefits > Risks and costs.

4. • Criteria for Test:
- Reliable
- Valid
- Simple and inexpensive
- Very safe
- Acceptable to subjects
- Cost effective
- Exit Strategy

5. • Exit Strategy:
- Facilities for diagnosis and appropriate treatments should be
available for positive subjects.

6. - Test should be acceptable to aimed people .
Test should not be:
- Painful
- Unsafe
- Discomforting or embarrassing
• Acceptability:

7. ● Also known as Repeatability, Reducibility & Precision.
● Getting the same results, when the test repeated in same target
individuals in the same settings .
• Reliability:

8. - Observer variation
- Subject variation (Biological)
- Errors related to technical methods
• Causes of Unreliability:

9. Observer Variation
Intra Observer Inter- Observer

10. • Also called within observer variation
- Same observer
- Two measurements
- Same Person
- Different results
• Intra-observer:

11. • Inter-observer:
Also known as between observer variation
- Same subject
- Different observers
Eg. :- Examination of blood smear for malarial
parasite by two observers

12. Subject variation
(Biological)
Changes in the
parameters
observed
Variation in how the
patient perceives the
symptoms
Regression to
mean

13. • Errors related to technical methods :
- Defective Instruments
- Error in calibration
- Faulty reagents
- Test itself might be inappropriate or unreliable
• When the errors are large, repeatability will be reduced, a
single test result may be unreliable.