Likelihood ratios as a measure of the diagnostic usefulness of excretory urogram information.

The log likelihood ratio (LLR) method of assessing physicians' diagnostic judgments can be used to measure the diagnostic usefulness of radiologic information (urography in this study). The method requires collection of referring pbysicians' diagnosis prior to and after urography and their certainty in relation to receipt of the radiologic information. Physicians in daily practice are able to provide diagnoses and assign a percentage number to their certainty. The LLR method permits measurement of the diagnostic usefulness of both normal and abnormal urogram results. Retrospective chart review does not provide the same LLR results as those obtained from the prospective study.