Basics of diagnostic evaluation part 2

Abstract

Despite a long tradition of reporting diagnostic accuracy in terms of sensitivity and specificity, only a minority of physicians correctly interprets and applies this information. Likelihood ratios (LRs) are more intelligible and more meaningful because it connects the preprobability of a person to postprobability that guide the physician to make the right decision about further procedures. Using Fagan Nomogram, makes the application of the LRs more customized to each case. In case of testing a continuous diagnostic test, receiver operating curve is used to set a cut-off value that will be the line between disease and nondisease persons. When determining the cut-off, the trade-offs between increasing the sensitivity with lowering specificity and vise-versa depends on the nature of the disease, as well as whether this test will be used as screening or as diagnostic.

Keywords

• Diagnosis
• likelihood ratio
• preprobability
• receiver operating curve