Screening test model using duration of labor for the detection of postpartum urinary retention.

Aims To construct a screening test model for postpartum urinary retention (PUR), using the duration of labor, which was shown to be the risk factor for PUR. Methods A group of 691 consecutive patients were recruited at postpartum day 1. Of the 691 patients, 101 (14.6%) had PUR. The 691 patients were computer-randomized into two groups, ‘A’ and ‘B.’ A receiver operating characteristic (ROC) curve was constructed for Group A to determine the optimum cutoff value for screening PUR using the duration of labor. The cutoff value was then applied to Group B to determine the screening test characteristics of the duration of labor: sensitivity, specificity, predictive values, and likelihood ratios. Results An ROC curve with an area under curve (AUC) of 0.63 (95% CI 0.57–0.69, P < 0.0001) was constructed. A range of cutoff values (with specificity ranging from 0.60 to 0.99) for the duration of labor was determined and the test characteristics computed. According to the test characteristics the optimal cutoff value for the duration of labor was 700 min. This cutoff value for the duration of labor has a specificity of 0.95, negative predicative value of 0.86, and likelihood ratio for a positive test of 0.88. Conclusion A screening test model using the duration of labor can be constructed to predict PUR. © 2005 Wiley-Liss, Inc.