Summary
An international collaborative exercise has been undertaken to calibrate a secondary
international reference preparation (IRP) of thromboplastin on behalf of the International
Committee for Standardization in Haematology (ICSH). This preparation of British Comparative
Thromboplastin (BCT/441) is required because supplies of the WHO primary IRP (BCT/253)
are necessarily limited.
The calibration was performed at seven centres with only a small degree of interlaboratory
variation. As a result of this study an ISI value of 1.04 has been assigned to the
preparation.
Opportunity was also taken to assess the reliability of a simplified calibration based
on lyophilised plasmas. The results of the latter appeared reliable.
BCT/441 will be available to officially designated National Control Laboratories for
calibration of local thromboplastins to promote prothrombin time standardization in
oral anticoagulant control.
Keywords
Thromboplastin - International reference preparation - ICSH - Prothrombin time standardization
