Screening & Diagnostic

Study Notes

Screening Need: Epidemiological case finding is expensive. A two-phase approach is often used, with a cheaper initial phase followed by a more expensive detailed method. Questionnaires are often used in the first phase, with interviews used in the secondary phase.

Purpose: To detect potential disease indicators.
Target Population: Large numbers of asymptomatic individuals, potentially at risk.
Test Method: Simple, acceptable to patients and staff.
Positive Result Threshold: Generally chosen towards high sensitivity to avoid missing potential disease.
Positive Result: Essentially indicates suspicion of the disease, requiring confirmation.
Cost: Cheap; benefits justify costs as a large number of people must be screened.

Purpose: To establish the presence or absence of a disease.
Target Population: Symptomatic individuals needing diagnosis, or those with positive screening tests.
Test Method: Can be invasive and expensive, but necessary for definitive diagnosis.
Positive Result Threshold: High specificity is prioritized, focusing on accuracy and precision more than patient acceptability.
Positive Result: Provides a definite diagnosis.
Cost: Higher costs than screening tests, but may be justified.

Sensitivity: How well a test identifies those with the disorder. High sensitivity means the test is good at picking up people with the disorder.
Specificity: How well a test identifies those without the disorder. High specificity means the test is good at ruling out people who don't have the disorder.
Example: A test for depression. High sensitivity means the test will be positive in most people with depression; high specificity means the test will be negative in most people without depression.