Cap survey results for factor VIII assays (1977-1978).

This paper combines the data from the 1976, 1977, and 1978 CAP Surveys concerning factor VIII methods. The different instrument-reagent combinations are ranked according to precision and sensitivity. The results of questionnaires on specific assay technic from 1977 and 1978 are analyzed. The number of laboratories performing factor VIII assays has increased from 1976 to 1978. There was a poor correlation between precision and sensitivity in most systems. For any given system, there was considerable variation in precision from a normal factor VIII level specimen to a low factor VIII specimen. Certain technics, such as the dilutions on normal plasma used to construct the standard activity curve, show considerable interlaboratory variation. The need for standardization of factor VIII assay methods is evident from this study.