A Study On Biostatistical Methods Of Prenatal Screening For Down's Syndrome

The aim of the study is to calcuate the maternal serum level value in domestic normal pregnant woman, and to discuss the ways and formals to eliminate influence of the factors and to evaluate the cutoff value and the parameters of the double test for second trimester serum screening for Down's syndrome in China, which based on foreign theory and method for screening Down's syndrome. Another goal is to evaluate the performance of different project for screening in foreign country and to evaluate the cutoff value. The results can be used as guiding the down's screening in china.The statistical premises and conclusions about the MOM are discussed and are validated with the real screening data. The Gauss normality of the mom value is assumed for calculating the risk, the study also presents the method of the log-transform of maternal serum index before MOM-transform. The method of Johnson's SL transform is proved to be effective and feasible to improve the normality.Factors effecting on maternal serum index, such as maternal weight, height, twin, smoking are discussed in the research and the adjusting formulas for them are presented. The viewpoint that the adjusting for weight is more important than for height is proved. Many valuable formals for the weight adjusting are also showed in the study, most of which are the same as the international common formals in essence. It proves them to be valuable for application.The performance of the prenatal screening projects during 1988~2002 for Down's syndrome is evaluated by means of the Summary Roc curve analysis. The triple test using MSAFP, hCG, and uE3 is proved to be the most effective screening test and free Beta hCG can substituted Total hCG. in screening test for Down's syndrome. Theses results can provide the significant guide in the prenatal screening for Down's syndrome in china.Significantly, the effect of double test for second trimester serum screening for Down's syndrome in China is evaluated with simulation based on methods without golden standard. The estimate of cutoff value, the ROC, sensitivity and specificity are presented, which can be looked as reference for analogous research by the counterpart in china.