Summary
Standardization of the thromboplastin most commonly used for anticoagulant control
in The Netherlands has been achieved by the Dutch Reference Laboratory for Anticoagulant
Control. The system established for control indicates the performance characteristics
of each batch of thromboplastin in patients relative to a national calibration batch.
Calibration constants were assessed according to an ICTH/ICSH proposal and with a
reproducibility of approximately 2% (CV). With the use of a given calibration constant
of the International Reference Preparation of Thromboplastin (1.0) and after assessment
of the calibration constant of the National Reference Preparation in international
terms (0.93), the accuracy of calibration with the various modifications of the calibration
procedure is of the order of magnitude of 3% (CV). On the basis of the calibration
protocol, physicians will be provided with correlation tables containing, for their
convenience, prothrombin (thromboplastin) times in terms of the reference thromboplastin
(uniform, i. e., batch-independent, prothrombin times), conventional prothrombin activity
(percentages), and in due course with International Calibrated Ratios.* With this
approach current practice in the prescription of oral anticoagulants will be maintained.
Opportunity is given, however, to aim at internationally proposed therapeutically
optimal target values.
