Background: In a rapid point-of-care screening programme for chromosomal
anomalies, analysis of biochemical markers in maternal blood can now be accomplished
in a rapid time frame (less than 20 min). The need to leave whole blood samples some
10 min for coagulation and a further 5 min for centrifugation adds additional
processing time.
Methods: The possibilities for reducing this processing time were
investigated using various anticoagulated blood collection systems and the Kryptor
analytical platform. Plasma levels of α-fetoprotein (AFP), pregnancy-associated
plasma protein-A (PAPP-A) and free human chronic gonadotrophin β-subunit (β-hCG) were
compared with those in maternal serum.
Results: From the mean results from ten patients it was shown that use
of heparin plasma resulted in a statistically significant reduction in levels of
PAPP-A and that EDTA plasma reduced the levels of PAPP-A dramatically. For AFP,
levels in citrated plasma and EDTA plasma were also significantly reduced, whereas
levels of free β-hCG were not affected.
Conclusion: Use of alternative sample types for PAPP-A is not possible.
The sample of choice for first trimester screening using the Kryptor platform is
maternal serum.
