Transportation of maternal serum specimens for screening for chromosomal aneuploidies: effect of seasonal variations, distance, and freezing on the stability of the biological markers

Objectives: We studied the stability of maternal serum markers for screening for Down syndrome [alpha-fetoprotein (AFP), unconjugated estriol (uE3), total human chorionic gonadotropin (hCG), and free β-human chorionic gonadotropin] following transportation. Design and methods: For each gestational week between 14 and 18 weeks, we collected about 50 samples for each possible combination of three potential sources of variation during transportation: season (winter/summer), sample frozen/fresh (prior to analysis) and origin (local or referred in) for a total of 1845 specimens. Commercial assays were used (IMx, Abbott for AFP and total hCG; AutoDelfia and Wallac for free β-hCG and AFP; and radioimmunoassay Ortho-Clinical Diagnostics, for uE3). Results: Results of both total and free β-hCG were significantly higher when samples were collected during summer and when they were sent to the laboratory from extramural blood drawing sites (multifactorial ANOVA, p < 0.007). Conclusion: We conclude that both total and free β-hCG can be adversely affected during transportation. The resulting higher concentrations of these markers may increase the false positive rate of prenatal screening programs for aneuploidies.