Combining and comparing area estimates across studies or strata.

A method for combining and comparing medical tests across studies or strata is presented. The area under the receiver operating characteristic (ROC) curve is the parameter of interest to be used for comparison. The combined area is a weighted average of the areas under the curve in each study or stratum. A chi-square test for equality of areas across strata can be used to compare the areas. The power of the test is also explored. The methods presented are simple and require only knowledge of estimates of area and their standard errors. Either parametric or nonparametric estimates of the area can be used.