Bayesian Prediction of Down Syndrome Based on Maternal Age and Four Serum Markers

Screening tests have been designed to identify women at increased risk of having a Down syndrome pregnancy. These tests have no risks of miscarriage, but they are not able to determine with certainty whether a fetus is affected. Diagnostic tests such as amniocentesis, on the other hand, are extremely accurate at identifying abnormalities in the fetus, but carry some risk of miscarriage, making it inappropriate to examine every pregnancy in this way. Muller et al.(1999), compares six software packages that calculate Ds risk, concluding that substantial variations are observed among them. In this paper, we provide a Bayesian reanalysis of the current quadruple screening test, based on maternal age and four serum markers (afp, uE3, hCG and DIA), which suggests the need to reevaluate more carefully actual recomendations.