Blood products and related biologicals

Blood coagulation disorders

The WHO International Standards (IS) for the measurement of blood coagulation factors and inhibitors in plasma are used by manufacturers and reference laboratories to calibrate their secondary standards. This assures a correct diagnosis of clotting factor deficiencies and monitoring of treatment with certain plasma products such as in patients with haemophilia.

The unitage assignment of clotting factors and inhibitors takes into account an external reference point, namely the concentration in 1 ml of "average fresh human normal plasma". In the preparation of "average fresh human normal plasma" it is necessary to adhere to defined conditions for blood collection and to take care that the composition of the plasma pool (e.g. distribution of age, sex, blood groups, use of drugs etc.) is representative of the normal population.

The quality of the collaborative study to assign the unitage and the reproducibility of assay methods can be found in the respective Reports of the WHO Collaborative Studies.

Reference preparations are established for:

Blood coagulation factors:



The characteristics of all reference preparations as well as the information regarding establishment can be found in the WHO Reference Material section.

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