Identifying hypocoagulable states with a modified global assay of overall haemostasis potential in plasma

To test the sensitivity of the global assay of overall haemostasis potential (OHP) in detecting hypocoagulation, the OHP was assayed in plasma containing exogenous thrombin (0.04 IU/ml), tissue-plasminogen activator (330 ng/ml), Ca2+ and a platelet reagent. Commercial plasmas with factor II, V, VIII, IX, X, XI, XII or VII deficiency were mixed with normal plasma in different proportions to imitate different severities. Samples from patients with haemophilia and factor XII deficiency were also examined. No clot was found in the absence of factor II/factor X, indicating that the tiny dose of thrombin worked solely as a trigger for the intrinsic pathway activation. Changed levels of the investigated coagulants, apart from factor XII, influenced the outcome. OHPs were decreased in patients with haemophilia but were unchanged or even increased in those with factor XII deficiency. This modified OHP method may therefore be useful for estimating the bleeding tendency in haemophilic patients and to find suitable doses and intervals for prophylactic treatment. It may also be of use in investigations of the effect of antifibrinolytic drugs as well as for identifying a thrombotic tendency in patients with factor XII deficiency. For detection of other coagulation factor deficiencies, our investigations with the commercial plasmas suggest that the OHP assay is also valuable, especially when the intrinsic pathway of the coagulation cascade is impaired.