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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.

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No abstract

To evaluate the influence of heparin on spontaneous platelet aggregation (SPA) two groups of patients, one treated with heparin and the other without heparin, were compared. The frequency of SPA is highly increased in patients with prosthetic heart valves treated with heparin as compared to patients not treated with heparin. Thus, the high frequency of SPA in prosthetic heart valve carriers treated with heparin might be due either to the prosthesis itself or to heparin. In contrast, in patients with thromboembolic disease, SPA does not seem to be more frequent in heparin-treated than in untreated patients.