receiver operating characteristic curves plot the sensitivity of a measure on the y-axis and (1 minus the specificity) on the x-axis. The area under the curve, which ranges from 0 to 1, is a measure of the accuracy of a test. Screening instruments that identify cases significantly better than chance have area under the curves >0.5; an area under the curve <0.70 is considered to have low accuracy, an area under the curve between 0.70 and 0.90 shows moderate accuracy, and an area under the curve >0.90 indicates excellent test accuracy. We present continuous and dichotomized results at both the standard and optimal cutoff scores. Continuous measures identify an optimal cutoff score for screening positive for depression; dichotomous measures identify participants at high risk for depression. Differences between the area under the curves obtained from the dichotomized and continuous curves assess whether potential differences in scale performance were related to dichotomizing the scales at a suboptimal threshold value. Comparisons of area under the curves created by different measures on the same outcome data were conducted, with x2 statistics accounting for within-participant correlation. Because sensitivity and specificity estimates change in opposite directions when the cutoff score varies, the optimal cutoff score balances both sensitivity and specificity while maintaining the receiver operating characteristic curve as close to the left corner (ie, the point [0, 1]). We defined optimal cutoff scores by using a cutpoint rule (ie, the closest-to-[0, 1] criterion) that selects the shortest radius originating at the (0, 1) point and terminating on the receiver operating characteristic curve in the x–y plane. All analyses used Stata version 10.0 (Stata Corp, College Station, TX) and SAS version 9.2 (SAS Institute, Inc, Cary, NC) software. RESULTSOverall, 106 primiparous adolescent mothers contributed a total of 289 postpartum study visits. The median
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