2ND-TRIMESTER DIURNAL-VARIATION OF MATERNAL SERUM ALPHA-FETOPROTEIN, HUMAN CHORIONIC-GONADOTROPIN, AND UNCONJUGATED ESTRIOL - IS IT PRESENTAND DOES IT AFFECT THE PREDICTION OF A PATIENTS RISK FOR FETAL DOWN-SYNDROME

Both a cross-sectional and a longitudinal study were performed to inve stigate whether or not the collection time should be taken into consid eration when generating a patient's risk for fetal Down syndrome with multiple marker screening. Diurnal variations of third-trimester alpha -fetoprotein (AFP) levels and first-trimester human chorionic gonadotr opin (hCG) levels have been previously reported. In addition, large ep isodic fluctuations of conjugated and unconjugated oestriol (uE3) as w ell as a diurnal variation have also been reported in the third trimes ter. If the levels of these analytes routinely fluctuate during the da y, they could affect a patient's risk calculation for fetal Down syndr ome. The longitudinal study evaluated ten non-diabetic women who under went sequential sampling for AFP, hCG, and uE3. The cross-sectional st udy evaluated 1953 patients for these three markers whose time of samp ling was recorded between 8.00 a.m. and 5.59 p.m. Using either study d esign, no significant effect was seen in the median MOM levels of the screening analytes as a function of the time of day.