Protocol for the evaluation of automated blood coagulation instruments (coagulometers) for determination of the international normalised ratio.

Results of prothrombin time tests for the control of oral anticoagulant therapy, when using automated blood coagulation instruments (coagulometers), may not be the same as those obtained when using manual methods, and variation in coagulometer performance may affect clinical interpretation of data. The haematology advisory committee of the Institute of Medical Laboratory Sciences has recommended that coagulometers should be used for determination of prothrombin times only if it can be demonstrated that the results are valid when compared with those of a standardised manual method. A protocol for the evaluation of coagulometers, and details of the procedures, are given in this report, the main emphasis of which is on the assessment of instruments for determination of the International Normalised Ratio. Guidelines are also provided for the general use of machines of this type and for the assessment of safety. The principles of the protocol are applicable to other automated tests of blood coagulation.