Age-independent first trimester screening for Down syndrome: analysis of three modified software programs with 6,508 pregnancies

Abstract

Background: The conventional first trimester screening (FTS) method integrates maternal age into risk calculation. It was suggested that this concept increases the false-positive rate in older, and the false-negative rate in younger mothers.

Materials and methods: Six thousand five hundred and eight combined FTS with known fetal outcome underwent regular risk calculation with the software programs Pia fetal database (PIA) (GE-ViewPoint, GE Medical Systems), prenatal risk calculation (PRC) (Version 1.0.61, gmt/nexus), and JOY (Version 2.1, PET software). The results were mathematically modified as if generated with age-independent software (PIA(mod), PRC(mod), and JOY(mod)).

Results: 17 of 40 trisomy 21 cases were present in women younger than 35. A right shift in the mean maternal age of false-negative cases occurred in all programs (PIA: 30.00, PIA(mod): 32.00, PRC: 30.00, PRC(mod): 32.25, JOY: 30.00, JOY(mod): 34.50). The overall false-positive rate declined by -40.03% (PIA(mod)), -38.64% (PRC(mod)), and -37.50% (JOY(mod)) and in women over 35 (40) years by -72.37, -73.45, and -73.20% (-89.04, -90.33, and -90.56%), being then as high as in the other age groups.

Conclusion: First trimester screening would become reasonable in women over 40 years. However, women over 35 would also be more often affected by false-negative results. The implications of a concept adaptation should be analyzed in a large prospective study.