| Table 1: Data on use of maternal serum screening for detection of Down syndrome from the Ontario Maternal Serum Screening Program* |
| Screening criterion or technique (risk cut-off 1/350) | Rate of false-positive results, % | Rate of detection of Down syndrome, % | No. of amniocentesis procedures performed to detect one case of Down syndrome |
| Age | 11.9 | 39.8 | 202 |
| Age plus maternal serum alpha-fetoprotein level | 12.3 | 49.8 | 166 |
| Triple serum markers | 9.5 | 735 | 87 |
| *Source: Gerry Dimnik, Manager, Ontario Maternal Serum Screening Database, Toronto: personal
communication, 1996. |