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[Comparative multicenter study of a rabbit high-sensitivity thromboplastin and a recombinant thromboplastin with
F Martínez-Brotóns1, M Borrell, J Fontcuberta
1Ciudad Sanitaria de Bellvitge, Barcelona.
Purpose:
The purpose of the present study was to compare the results obtained with a human recombinant thromboplastin (Innovin, Baxter) (IN) and a high-sensitivity rabbit brain reagent (Thromboplastin IS, Baxter) (IS), on the performance of prothrombin time (PT) test and the functional assay of factors included in the extrinsic coagulation system, in order to establish possible differences on imprecision, diagnostic accuracy and sensitivity to the oral anticoagulant defect, between the two products.
Material And Methods:
Six Spanish hospital took part in the study. Plasma samples from 221 healthy subjects, 100 patients with severe liver disease, 27 with dysfibrinogenaemia, 10 with lupus anticoagulant and from 13 individuals propositus and their relatives with congenital deficiencies of the extrinsic coagulation pathway, and their relatives were studied; 188 patients stabilized on oral anticoagulant therapy and 82 on heparin therapy were also included. The in vitro effect of heparin was tested by addition of increasing amounts of heparin (0.3 to 10.0 IU/mL) to aliquots of normal plasma.
Results:
Both in the intra-assay and in the inter-assay imprecision study, a better coefficient of variation was obtained with IN when the PT was performed on abnormal samples. Prothrombin time ratio from patients with liver disease had significantly higher values with IS. On the contrary, IN had a higher sensitivity in samples from patients with dysfibrinogenaemia or from those stabilized on oral anticoagulant therapy. In showed a very low sensitivity to heparin at concentrations corresponding to the therapeutic range.
Conclusions:
The results of this field study indicate that IN, compared with a high-sensitivity rabbit brain thromboplastin, is a suitable reagent for PT determination in normal subjects, patients with liver disease or with congenital deficiencies of clotting factors. It shows a higher sensitivity in cases of dysfibrinogenaemia and in patients on oral anticoagulant therapy. In addition, the recombinant reagent had better reproducibility when the PT was performed on abnormal samples, and it was hardly affected by heparin within the therapeutic range.