Collaborative calibration of a national standard thromboplastin

Abstract

International Reference Preparations (IRP) of Thromboplastins available from the Bureau Communautaire de Référence (BCR) of the European Communities are expensive and inconvenient to import. Therefore, we endeavoured to produce a locally acceptable National Standard Thromboplastin (NST01). Samples of the stabilized, lyophilized human brain thromboplastin and IRP 67/40 (BCR 099) were sent to eleven major laboratories who were willing to participate in the Australia-wide calibration. Testing was carried out according to the guidelines of the International Committee on Thrombosis and Haemostasis. A panel of four lyophilized, oral-anticoagulant patient plasmas was included for testing as a means of monitoring inter-laboratory variation. Each participating laboratory was instructed to test both the NST01 and the BCR thromboplastins simultaneously on sets of fresh normal plasmas and stable Warfarin patient plasmas (as well as on the lyophilized plasmas provided). The resulting International Sensitivity Index (ISI) of NST01 was calculated as 0.952±0.008. This National Standard preparation is now available from the Australasian Reference Thromboplastin Unit (along with the series of Reference patient plasmas) for use by laboratories to improve inter-laboratory comparability of prothrombin time results.