The effect of sample preparation and storage on maternal triple-marker screening

Abstract

To evaluate the effect of different sample collection, storage, and preparation techniques on serum alpha-fetoprotein (AFP), beta-hCG, and unconjugated estriol (E3) concentrations. A solution containing known concentrations of AFP, hCG, and unconjugated E3 was diluted in blood samples obtained from seven healthy male volunteers. Serum from each blood sample was removed immediately, and either assayed or frozen at -70C. Portions of the remaining blood were handled as follows: centrifuged and refrigerated, centrifuged and left at room temperature, not centrifuged and refrigerated, or not centrifuged and left at room temperature. Serum was removed from these samples for triple-marker analysis at 24, 48, 96, and 168 hours after the initial sample collection. Immediate freezing of serum and subsequent thawing resulted in a significant increase in beta-hCG and unconjugated E3 levels, but no change in AFP levels. There was a significant effect over time on AFP, hCG, and unconjugated E3 concentrations. The change in AFP levels was influenced by centrifugation status, whereas all three analytes were influenced by refrigeration status. Different sample collection, storage, and preparation techniques may affect maternal triple-marker screening.