Objectives: In February 2007, the "Fetal Medicine Foundation Germany (FMF-D)" introduced its new calculation software for First Trimester Screening (FTS), called "Prenatal risk calculation (PRC)". The aim of this study was to retrospectively investigate the test performance of PRC in comparison to the "NT module of the JOY software (JOY)".
Methods: A total of 3,516 combined first trimester screenings from 11 + 0 to 13 + 6 weeks of gestation were accomplished according to the FMF-standard. Adjusted risk calculation for aneuploidy was performed with PRC and JOY.
Results: A total of 2,202 complete data sets of singleton pregnancies were analyzed, including 10 trisomy 21 cases, 4 trisomy 18 cases, and 1 trisomy 13 case. Risk calculation with PRC and JOY showed highly significant results (P value<0.0001). JOY attained, at a cut-off of 1:300 (sensitivity 82.4%, false-positive rate 3.6%, positive predictive value 15.2%) and at a cut-off of 1:230 (82.4, 2.4, 21.2%), a better test performance in comparison to PRC (76.5, 7.1, 7.7% and 76.5, 5.3, 10.2%, respectively). The differences were highly significant (P value<0.0001).
Conclusion: In this preliminary study, PRC demonstrated highly significant results in detecting aneuploidies in FTS. However, in comparison to JOY, its test performance was significantly inferior. A twice higher false positive rate would have doubled unnecessary invasive testing in a prospective setting. We therefore recommend a methodical revision of PRC.