Fifteen years of triple tests in The Netherlands; the life cycle of a screening test

OBJECTIVE: This report provides an overview of 15 years prenatal screening for Down syndrome (DS). METHODS: Between 1991 and 2005, blood samples for the triple test were sent for analysis to our laboratory. Test results were considered screen-positive for neural tube defects (NTDs) if the serum alpha-1-fetoprotein > or = 2.50 MoM for singleton pregnancies or screen-positive for DS if the calculated risk was at least 1 in 250. RESULTS: As many as 42 554 tests were performed. Data on the pregnancy outcome were available for 30 290 screening tests (71.2%). In 1991, most requests (93%) came from the university hospitals; thereafter a shift toward midwives occurred. Until 2001, the number of requests rose to 3500 a year. Most samples were collected between 15 and 17 weeks of gestation. The median age of women for whom a test was requested increased from 30.5 to 34.5. The detection rate (DR) for DS remained stable over the years (80%), with a false positive rate of about 13%. The DR for Trisomy 13, 18, and NTD was 50, 68, and 70%, respectively. CONCLUSION: Based on the results of this study, the triple test may be considered a fairly good second trimester screening test. Here it is shown that health practitioners got more acquainted with the test through the years. This may have served the swift introduction of a formal national screening program that started in January 2007.