B8.045 Prenatal Screening EBM Flashcards
screening test
identifies patient at risk for condition
characteristics of a screening test
highly sensitive: can rule OUT condition
if positive, followed up with a diagnostic test
diagnostic test
determines presence of condition
characteristics of a diagnostic test
confirmatory test as follow up to screening test
suggestive clinical signs/symptoms present
highly specific (typically): rule in condition
what is a false positive rate
1-specificity
FP/(TN+FP)
specificity
probability of having negative test given that the disease is not present
TN/(TN+FP)
how do you make a flippin 2x2 table
disease on TOP
test on SIDE
counseling if positive screening test
increased risk of having the condition
-counsel and offer option of diagnostic testing
counseling if negative screening test
lower post test probability of having the condition
- counsel on lower risk
- DO NOT offer additional screening (increased risk of FPs)
- diagnostic test later if indicated by additional findings
likelihood ratio formula
likelihood of a test result when disease is present / likelihood of a test result when disease is absent
function of LR
expresses how much more (or less) likely test result is to be found in diseased (compared to non diseased) people
how do you determine posttest probability
pretest probability and LR
LR positive formula
sensitivity/ (1-specificity)
LR negative formula
(1-sensitivity)/ specificity
how to interpret LR values
if LR=1 test has no discriminatory value
if LR+ > 10, then test has high diagnostic value
if LR- <0.1, then test has high diagnostic value
