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 beta-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 beta-hCG and AFP; and radioimmunoassay Ortho-Clinical Diagnostics, for uE3).

RESULTS

Results of both total and free beta-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 beta-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.