Abstract

A study has been made to determine whether a reliable comparison can be made between the British Comparative Thromboplastin and Thrombotest using the nationally adopted standardization procedure. The method recommended appeared sufficiently satisfactory and statistically valid for the comparison between the British Comparative Thromboplastin and Thrombotest.

The degree of diversion in the location of the `best lines', which should have been in an identical position at each centre, suggests that the standardization procedure at individual hospitals with Thrombotest is not usually a sufficiently reliable basis for clinical anticoagulant dosage. The degree of diversion almost certainly arises from technical error in the standardization procedure, and it is suggested that Thrombotest should be calibrated against the British Comparative Thromboplastin only in specialist coagulation centres thoroughly conversant with both techniques.