THE EFFECT OF SAMPLE PREPARATION AND STORAGE ON MATERNAL TRIPLE-MARKER SCREENING

Objective: To evaluate the effect of different sample collection, stor age, and preparation techniques on serum alphafetoprotein (AFP), beta- hCG, and unconjugated estriol (E3) concentrations. Methods: 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 assay ed or frozen at -70C. Portions of the remaining blood were handled as follows: centrifuged and refrigerated, centrifuged and left at room te mperature, not centrifuged and refrigerated, or not centrifuged and le ft at room temperature. Serum was removed from these samples for tripl e-marker analysis at 24, 48, 96, and 168 hours after the initial sampl e collection. Results: Immediate freezing of serum and subsequent thaw ing resulted in a significant increase in beta-hCG and unconjugated E3 levels, but no change in AFP levels. There was a significant effect o ver time on AFP, hCG, and unconjugated E3 concentrations. The change i n AFP levels was influenced by centrifugation status, whereas all thre e analytes were influenced by refrigeration status. Conclusion: Differ ent sample collection, storage, and preparation techniques may affect maternal triple-marker screening.