Stability of first- and second-trimester serum markers after storage and shipment

Objective The purpose of this study was to examine the levels of first- and second-trimester maternal serum markers used in Down syndrome screening in relation to the time between sample collection and arrival at the laboratory. Methods The FASTER trial, designed to compare first- and second-trimester screening tests for aneuploidy, has recently been completed, having recruited more than 38000 patients. According to the trial protocol, all blood samples were drawn in serum separator tubes, centrifuged within 30 min and stored at 4 degrees C until shipment by air express. To examine the effect of delayed shipment, serum marker levels (expressed as multiple of the median-MoM) were evaluated in the first- and second-trimester samples and stratified by the number of days between serum collection and laboratory receipt. Results Under specified collection and shipment conditions, first and second-trimester screening marker mean levels and degrees of variance were stable for up to 9 days, with the exception of unconjugated estriol, which was stable for up to 6 days. Conclusion The levels of first- and second-trimester Down syndrome screening markers can be measured reliably when the sample is centrifuged, refrigerated until shipment and received in the laboratory within a week of being drawn. A conservative approach would be to restrict testing to within 6 days of draw, with the intent to keep shipping delays to a minimum. Copyright (c) 2006 John Wiley & Sons, Ltd.