screening test Flashcards
screening test
procedure which enables to predict the absence or presence of a disease from knowledge of test results
2 dimensions of screening tetsts
appropriateness to detect the disease
diagnostic power
biomarker
a measure that tells us information about a disease
criteria for using a screening test
- the significant burden of a disease in a population
- the preclinical stage is detectable and prevalent
- early detection improves outcome
- acceptable to population, inexpensive and relatively accurate
requirements for screening test to identify biomarkers
- test must be quick, easy, and inexpensive
- must be safe for patients, physicians
- sensitivity, specificity, and predicted values must be known and acceptable
- adequate follow up for screened positive
aim of screening tests
-minimise the probability of error
-maximise the probability of true positive and true negative
false discovery rate (alpha)
FDR= 1-PPV
what happens as the prevalence of a disease increases
the PPV of the test increases and the NPV decreases
curva ROC
finding a threshold= optimal combination of specificity and sensitivity
purpose of ROC
- finding optimal threshold- optimal point
- finding optimal test type
screening level
how good the test discriminated is proportional to subarea
screening level equation
z= AUC= 0.5/squareroot sigma2AUC