OBJECTIVETo develop a method for evaluating the feasibility of prenatal screening using local median value and determining the cut-off value.

METHODSWith receiver operating characteristic curve (ROC) analysis, results of second trimester prenatal screening calculated by a local median value in a new model and the built-in median value in 2T software were compared. The cut-off value was set by serial analysis of true and false positive rates and other relevant data.

RESULTSThe ROC curve has accurately estimated the difference in the screening efficacy between a local median value and that embedded in the 2T model, and established a reasonable cut-off value for the laboratory based on false positive rate and detection rate.

CONCLUSIONThe method of ROC curve can be used to evaluate the performance of local median value in prenatal screening and to test the rationality of cut-off value established in the laboratory. As the result, a better cut-off value may be derived.