# step II

 Sensitivity finds disease ...best used to screen Excludes disease if test negative, Includes disease is test is positiveTP/TP+FN Specificity How good in normal populationused to confirm diseaseTN/TN+FP Reference interval +/- 2SD = 95% of normal Negative Predictive Value How likely the negative result is a true negative and not a false negative- with a 100% sensitive test = 100% b/c there are no false negatives-with a 100% specific test = could be TN or FN does not exclude disease-TN/TN+FN Highly sensitive test ...increases prevalance of disease Increasing upper limit of normal of a test reference interval increases specificity and PPVdecreases sensitivity and NPV decreasing upper limit of normal on test reference interval increases sensitivity and NPVdecreases specificity and PPV Prevelance Prevelance = incidence x durationTP+FN/ TP+FN+TN+FP -prevelance is how many people have the disease right now. It increases as the duration of a disease increases. -incidence is how many people develop a disease in a population over a set time, usually one year. Positive predictive value how likely a positive result is a true positive -TP/TP+FP-100% sensitive test = result could be TP or FP includes people with disease but does not confirm-100% specificity = 100% b/c there is no false positives, confirms disease! Authorhartman.elizabeth ID23975 Card Setstep II DescriptionHY fact review Updated2010-06-18T02:14:53Z Show Answers