Multicenter Study Of Second-trimester Screening For Down Syndrome In Dried Blood Spots

ObjectiveThis is a multicenter research to evaluate the feasibility and the methodology of dried bloods spots (DBS) as a method for Down syndrome (DS) screening. To compare the correlation of the two prenatal screening programs--DBS and serum. And to set up the curve of median-weeks, and to obtain the cutoff value, and to establish second-trimester screening for Down syndrome in dried blood spots.Materials and Methods1. The serum and DBS samples of gravidas were collected from the obstetric clinics of yunnan province first people's hospital, maternity and child care centers of shaanxi province, sichuan university huaxi medical center hospital, the maternity and child care centers of hunan province, maternity and child care centers of haidian district Beijing city from April2011to Sept2011. The gestational week of all the gravidas was between15to20+6weeks, and record the relevant clinical information simultaneously.2. To discuss the detection precision and sensitivity of DBS, and the selection of drilling position.3. AFP, free β-HCG concentrations were measured for all the serum and DBS samples to set up the the curve of median-weeks.4. Follow-up the pregnancy outcome.5. Correlation of all parameters between DBS and serum were compared. The detection rates of DBS and serum prenatal screening program were compared, and their correlation was evaluated. To get the cutoff value of DBS DS screening.Results1. In this study, the precision detection of DBS control within15%, The functional sensitivity of AFP and free-β-HCG in DBS were1.2u/ml,5.9ng/ml, and the low limit of detection of AFP and free-β-HCG in DBS were0.27u/ml,0.57ng/ml.2. A total of10252cases were collected, the measurement values of three certer were accordance, the distribution of age and weight in three certer were different. The MoM value of free β-HCG and AFP distribution in DBS were described as unimodal curves.3.7685cases were followed up, follow-up rate was75%, the rate of follow-up in specimen collection centers were inconsistency. A total of64Fetal congenital anomaly was found, DS10cases,18-trisom1cases, NTD2cases.4. When DS screening cutoff value was seted to1/270, the performance of DBS screening program was moderate consistent with that of the serum screening program, Kappa coefficient was0.511. The detection rate of DBS DS screening was60%, false-positive rate was4.96%; and for serum DS screening, the detection rate was80%, false-positive rate was8.26%. The screening efficiency of each specimen test center were different. AUC of serum method (0.927) were larger than that of DBS method (0.813), the diagnostic value of the DBS was inferior than the serum method.ConclusionsDS prenatal screening in DBS is feasible. But it excisted differences between DBS screening system and serum system. The application of DBS screening system in various regions was different, still need to establish their own median-weeks (days) curve, to calculation suitable cut-off value.