Repeated measures screening for Down's Syndrome.

OBJECTIVE To demonstrate the potential value of screening for Down's Syndrome using highly correlated repeated measures of serum markers taken in the first and second trimesters of pregnancy. DESIGN A Monte Carlo simulation study. POPULATION Detection rates and false positive rates relating to the maternal age distribution of England and Wales for the period 1996 to 1998 were obtained using marker distributions from the SURUSS study. RESULTS Screening using first trimester nuchal translucency and repeated measures of uE3 and PAPP-A in the first and second trimester has an estimated false positive rate of 0.3% for an 85% detection rate. This should be compared with the integrated test with an estimated false positive rate of 1.2% for the same detection rate. CONCLUSIONS The performance of repeated measures screening tests, and their acceptability to women, should be assessed in further prospective studies.