Summary
Monitoring of anti-factor Xa activity is often performed during treatment with low-molecular-weight
heparins (LMWHs) in pregnancy because the anticoagulant effect may decrease as pregnancy
progresses, but assays for anti-factor Xa activity are unavailable in many clinical
institutions caring for pregnant women. Heptest-STAT is a new clotting assay for monitoring
of LMWHs, which has been optimised for use in near-patient laboratory instrumentation.
It has been suggested that monitoring of LMWHs requires the use of individual calibration
curves for each LMWH.We compared the dose response of four conventional LMWHs and
fondaparinux in normal plasma, and plasma from women in first, second and third trimester
of pregnancy. Three concentrations of LMWHs, fondaparinux, or unfractionated heparin
were added to pooled plasma samples from nonpregnant women (n=10), and pregnant women
in first (n=10), second (n=10) and third (n=10) trimester of pregnancy. Heptest results
are not influenced by the stage of pregnancy. In contrast, dose-related aPTT prolongation
declines during pregnancy. All LMWHs tested, as well as fondaparinux, display a similar
doseresponse in Heptest compared to the chromogenic anti-factor Xa assay. Heptest-STAT
can be used with the same standard calibration for non-pregnant and pregnant patients
and for all LMWHs under investigation, including fondparinux. No individual calibrations
are necessary.
Keywords
Heparins - LMWH - pregnancy - heptest - fondaparinux - monitoring
