Proposal for a general strategy of standardization of fibrinolysis assays to be used in clinical practice

During the last decade there has been a growing interest within clinical medicine in studying quantities of the fibrinolytic system and a number of methods has been disseminated to clinical laboratories. Although, the nomenclature and the units of a number of fibrinolytic quantities have recently been defined and accepted within the framework of ISTH, IFCC and IUPAC, there is still unacceptable incompatibility of the measurements between methods and laboratories and thus a poor transferability of the data from one laboratory to another. This has been illustrated in studies which compare different methods for determination of plasminogen activator inhibitor 1 activity (Gram et al. Thromb Haemost 1993; 70: 852-7). The standardization within the field of fibrinolysis has so far exclusively made use of the availability of a number of different matrix reference materials in which the assignment of values is primarily based on consensus values obtained by non-standardized methods. So far no reference methods nor definitive methods exist for analytes in the fibrinolytic system. We propose that action should be taken to ensure adherence to a comprehensive reference measurement system such as that used in clinical chemistry. As a supplement to available reference material, reference candidate methods with well-defined and controlled specificity should be established as a first step. Also, analytical goals should be defined which are based on data on biological variation in healthy individuals.