How Do You Calculate Sensitivity, Specificity, Positive Predictive Value, And Negative Predictive Value?
• Define a population to sample, e.g. 1000 patients in a clinic. • Define the disease or characteristic of interest, e.g. syphilis. • Have a well-established gold standard test to determine the prevalence of disease or characteristic, e.g. darkfield microscopic documentation of presence of the Treponema pallidum bacteria from scrapes off a syphilic sore, in collaboration with clinical findings. Use the gold standard test to determine who has the characteristic and who does not. For illustration, let us say 100 people have it and 900 do not. • Have a test that you are interested in determining its sensitivity, specificity, positive predictive value, and negative predictive value for this population, and run this test on everyone within the chosen population sample. For example, let this test be a rapid plasma reagin (RPR) test to screen for syphilis. Use it to test the 1000 people in the sample. • For people that have the characteristic (as determined by the gold standard), record the n
