Overview Diagnostic testing performance is measured in a variety of ways Sensitivity and specificity describe the frequency of test results by disease status Positive and negative predictive value describe the frequency of disease status by test result Precision and accuracy describe different types of variation in test results Sensitivity, Specificity, Positive Predictive Value, and Negative Predictive Value These 4 measures describe how well diagnostic tests capture the true presence or absence of disease Predictive value changes with disease prevalence, sensitivity and specificity do not A 2x2 contingency table can help with calculations login to view 22 more bullets Cut-off point for positivity may be adjusted to optimize sensitivity and specificity for different purposes, which are inversely related (cut-off point with decreased sensitivity is associated with increased specificity and vice-versa) Receiver operating characteristic (ROC) curves are a graphical depiction of a test's overall diagnostic performance login to view 8 more bullets Likelihood Ratios (LRs) Also used to assess diagnostic test performance in isolation or in sequence Does not change with disease prevalence Represents the probability of a patient with a disease having a positive or negative test result in comparison to the probability of a patient without the disease having a positive or negative test result Positive LR login to view 7 more bullets Negative LR login to view 7 more bullets Precision and Accuracy Precision login to view 4 more bullets Accuracy login to view 2 more bullets