RESUMO
BACKGROUND: In this study we aim to investigate the stability of free-beta-hCG and PAPP-A over time in serum and whole blood in typical routine temperatures. METHODS: Serum pools were stored under the following temperatures: 30 degrees C, room temperature, refrigerator temperature and -20 degrees C, for up to 240 days. Stability of the markers in whole blood was examined in a shorter study and compared to serum. Samples were analysed using the AutoDELFIA and DELFIA Xpress analysers. RESULTS: On the AutoDELFIA, considering a 10% change acceptable, PAPP-A levels are stable in serum for 142 days at refrigerator temperature, 37 days at room temperature and 20 days at 30 degrees C. Free-beta hCG is stable in serum for 94 days at refrigerator temperature, 3 days at room temperature and 12 h at 30 degrees C. There was no significant change with either analyte after -20 degrees C storage for up to 240 days or after six repeated freeze-thaw cycles. In whole blood, free-beta hCG levels increased more rapidly compared to serum, especially at 30 degrees C. CONCLUSION: Normal handling of samples is only likely to minimally effect the risk assessment of chromosomal anomalies. However, careful attention should be paid to minimise the increase of free-beta hCG levels in samples shipped as whole blood.
