Laboratory monitoring of a low molecular weight heparin (enoxaparin) with a new clotting test (Heptest).

A new simple clotting test (Heptest) for low molecular weight heparins was compared to anti-Xa determination by an amidolytic assay in volunteers and in patients receiving standard calcium heparin or low molecular weight (LMW) heparin (Enoxaparin) by subcutaneous administration. The results obtained with both methods are in very good agreement. It seems that the Heptest, although influenced by various other clotting parameters, is nevertheless relatively specific for anti-Xa activity. Despite our positive first impression, we object to expressing the results in micrograms of heparin per milliliter or anti-Xa units. Until rigorous standardization is possible, we prefer to express the results as clotting times. Preliminary results warrant a more extensive study in order to assess the clinical relevance of Heptest in patients receiving unfractionated or LMW heparins.