Monitoring of heparins in haemodialysis using an anti-factor-Xa-specific whole-blood clotting assay.

In haemodialysis low-molecular-weight (LMW) heparin is increasingly used for anticoagulation. The advantages over unfractionated (UF) heparin are the lower bleeding risk and the lack of influence on lipid metabolism. However, no reliable and rapid method is available so far to control the efficacy and safety of LMW heparin during haemodialysis. The specific anti-factor Xa (aXa) chromogenic substrate assays are laborious and time consuming. In the present study we have compared chromogenic assay with a coagulation assay (heptest), which was performed from plasma and whole-blood samples. The effects were compared with unfractionated heparin during haemodialysis. The aXa activity in the chromogenic S2222 assay ranged between 0.2 and 0.5 U/ml with UF heparin and between 0.4 and 0.8 U/ml with LMW heparin during haemodialysis. The coagulometric aXa activity in heptest assay from plasma was 0.6-1.0 U/ml with UF heparin and 1.2-2.0 U/ml with LMW heparin. The Heptest coagulation values from citrated whole blood samples ranged from 0.4 to 0.8 U/ml with UF heparin and from 0.8 to 1.4 U/ml with LMW heparin. The prolongation of the heptest clotting times with UF and LMW heparin was in the range of 4.4 for UF heparin and 5.2 for LMW heparin using the whole-blood assay. Heptest assay from plasma samples yielded prolongations of 6.1 with UF heparin and 6.6 with LMW heparin. The data show that the coagulation assay is rapid and reproducible using plasma or uncentrifuged whole-blood samples and is valid to monitor UF heparin or LMW heparin in patients undergoing chronic intermittent haemodialysis.