POST: 4a Screening & Diagnostic PDF

**[Core Principles in Mental Health Research ]** **[POST: 4a Screening & Diagnostic ]** [The need for screening:] - Epidemiological case finding is expensive - Two phase approach - e.g., the national psychiatric morbidity study - Cheap 1^st^ phase/expensive 2^nd^ phase - Questio...

**[Core Principles in Mental Health Research ]** **[POST: 4a Screening & Diagnostic ]** [The need for screening:] - Epidemiological case finding is expensive - Two phase approach - e.g., the national psychiatric morbidity study - Cheap 1^st^ phase/expensive 2^nd^ phase - Questionnaire vs More detailed questionnaire - Questionnaire vs Interview [Diagnostic tests & Screening tests:] screening tests Diagnostic tests --------------------------- ------------------------------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------------------------------------- purpose To detect potential disease indicators To establish presence/absence of disease target population Large numbers of asymptomatic, but potentially at-risk individuals Symptomatic individuals to establish diagnosis, or asymptomatic individuals with a positive screening test test method Simple, acceptable to patients and staff Maybe invasive, expensive but justifiable as necessary to establish diagnosis positive result threshold Generally chosen towards high sensitivity not to miss potential disease Chosen towards high specificity -- more weight given to accuracy and precision than to patient acceptability positive result Essentially indicates suspicion of disease that warrants confirmation Result provides a definite diagnosis cost Cheap, benefits should justify costs since large number of people need to be screened to identify small number of cases Higher costs associated with diagnostic test maybe justified to establish diagnosis [Sensitivity & Specificity: ] - Sensitivity: how well the test correctly identifies someone who has the disorder - E.g., is a person has depression, how often will the test be positive for depression - Specificity: how well the test correctly identifies someone who does not have the disorder - E.g., if a person does not have depression, how often will the test be negative [Calculating Sensitivity & Specificity:] - Before calculating the sensitivity and specificity you must know the correct disorder status - The most accurate test used for determining the presence/absence of a disorder is the "gold standard" - A 2x2 table is often used to compare the performance of the new test to the gold standard test [Sensitivity:] Gold standard gold standard ------------- --------------- -------------------- -------------------- Disorder + No Disorder - New measure Disorder + A (true positive) B (false positive) No Disorder - C (false negative) D (true negative) Sensitivity [= A. ] A + C Specificity = [D.] B + D