engleski

When screening for Down syndrome do we think about the preanalytics?

Background: On national level, only several specialized laboratories provide screening for Down syndrome. Our first aim was to confirm manufacturer claims that stability of free βhCG ( free beta-subunit of human chorionic gonadotropin ) and PAPP-A (pregnancy associated plasma protein A) in serum at room temperature is 8h. Requirements for sending samples by delivery service should depend on analyte stability. Most samples are being delivered within 24 or 48h. Our second aim was to investigate stability of free βhCG and PAPP-A in serum at room temperature within 24h and 48h. Materials and Method: Samples were collected from 30 women who came for Down syndrome screening in tubes with clot activator. Free βhCG and PAPP-A were measured (Roche Cobas e601) in primary samples: initially (I) and after 8h (II) and also in aliquoted samples: after 24h (III) and after 48h (IV) (all samples were stored at room temperature). Data were not normally distributed (Shapiro Wilk test) and were expressed as median (inter-quartile range). Differences between measurements were examined by Wilcoxon test. Results: Free βhCG median concentration in initially measurement was 51, 75 ng/mL (24, 17-70, 90), after 8h 53, 45 ng/mL (25, 58-74, 69), after 24h 53, 81 ng/mL ( 25, 30-75, 53) and after 48h 53, 52 ng/mL ( 27, 36-81, 35). PAPP-A median concentration in initially measurement was 3495 mUI/L (2108-6267), after 8h 3562 mUI/L (2100-6378), after 24h 3712 mUI/L (2195-6484) and after 48h 3928 mUI/L (2307-6275). Wilcoxon test showed statistically significant difference in free βhCG and PAPP-A concentration between (I) (II) (p<0, 001), (I) (III) (p<0, 001), (I) (IV) (p<0, 001). Conclusion: This study revealed that manufacturer claims about free βhCG and PAPP-A stability at room temperature within 8h are not confirmed. Also, free βhCG and PAPP-A concentrations increase after 24h and 48h at room temperature. Therefore, delivery protocol should be revised according to the investigated stability.

free βhCG, PAPP-A, stability, room temperature

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