Christensen R L, Triplett D A
Am J Clin Pathol. 1983 Oct;80(4 Suppl):633-42.
It has become apparent that mild factor deficiency states (i.e., Factor VIII, IX, and von Willebrand's syndrome) are frequent causes of postoperative bleeding and hemorrhagic complications following trauma. Despite their incidence, they frequently are not diagnosed or in some instances are misdiagnosed. In an attempt to improve the level of performance of factor assays, the College of American Pathologists recently has introduced factor-deficient plasmas into their proficiency testing program. Initially, plasmas deficient in Factor VIII were evaluated and more recently, plasmas deficient in Factors IX and XI were included. The results of the initial survey programs indicated a lack of precision and accuracy of Factor VIII and IX assays. Similar difficulties also were encountered with plasmas deficient in Factor XI. Extensive information also was gathered on the fundamentals of laboratory performance of factor assays. This information included data regarding preparation of the standard activity curves, source of deficient substrate plasmas, number of patient sample dilutions, etc. Also, it was evident that various thromboplastins have different degrees of sensitivity to the various deficiency states. A portion of this variability may be attributable to the choice of activator, however, it would appear that the phospholipid content of the partial thromboplastins is of equal importance.
