Comparative study on a new one-stage clotting assay for heparin and its low molecular weight derivatives.

The effects of a normal and a low molecular weight (LMW) heparin fraction were compared by four coagulation methods. Plasma samples of patients were investigated who were treated with normal heparin or with a LMW heparin. The study was undertaken to analyze the interrelationship between the coagulation methods: Heptest, activated partial thromboplastin time, thrombin clotting time, and S 2222 chromogenic anti-factor Xa test. The results showed a high correlation between Heptest and S 2222 anti-factor Xa method for unfractionated and LMW heparin (r = 0.91 and 0.90). Comparing the coagulation times in seconds of Heptest and aPTT, the correlations were r = 0.56 (normal heparin) and 0.15 (LMW heparin). The correlation between the coagulation times of Heptest and thrombin clotting time were r = 0.65 and 0.25, respectively. The correlations between the coagulation methods were higher, when coagulation times rather than transformed values to units per liter of the Heptest and of the S 2222 anti-factor Xa method were employed. Furthermore, the data demonstrate a high sensitivity of the Heptest to conventional and LMW heparin, whereas activated partial thromboplastin time and thrombin clotting time are less sensitive to either heparin. For laboratory control of LMW heparin, Heptest and S 2222 chromogenic method are reliable tests. Therapeutic ranges will have to be established.