Diagnostic accuracy of four assays of prostatic acid phosphatase. Comparison using receiver operating characteristic curve analysis

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Abstract
The diagnostic characteristics of 4 assays of prostatic acid phosphatase (for the detection of prostatic carcinoma) by 2 methods. In the 1st analysis, receiver operating characteristic (ROC) curves were developed and the areas under the curves were calculated. In the 2nd analysis, the sensitivity of each assay was compared with the sensitivities of the other assays with specificities set at equal levels. One or more assays were performed in 1298 patients; 141 underwent all 4 assays. Pairwise comparisons of the areas under the ROC curves showed no significant differences. No differences were found in the sensitivities of the 4 assays when the upper limits of normal were selected to provide equal specificities. Apparently, there is little difference in diagnostic accuracy among the prostatic acid phosphatase assays. These findings contrast with previous studies that used only one upper limit of normal and that found some assays to be superior to others. Receive operating characteristic curve analysis corrects for the bias introduced by the choice of an upper limit of normal.