Article: PDF OnlyVariability in plasma prothrombin concentration implications for use in epidemiologySmiles, A. M.; Macy, E. M.; Sakkinen, P. A.; Bovill, E. G.; Mann, K. G.; Tracy, R. P.Author Information A. M. Smiles, E. M. Macy, P. A. Sakkinen and E. G. Bovill are with the Department of Pathology, University of Vermont; K. G. Mann is with the Department of Biochemistry, University of Vermont, and R. P. Tracy is with the Departments of Pathology and Biochemistry, University of Vermont, Colchester, Vermont, USA. Blood Coagulation & Fibrinolysis: September 1998 - Volume 9 - Issue 6 - p 525-532 Buy Abstract Recent evidence suggests a major role for prothrombin as a risk factor for thrombosis. However, estimating prothrombin levels from a deficient plasma-based clotting assay (factor lie) is expensive and technically difficult in the setting of population-based research. We report the development of an enzyme-linked immunosorbent assay (ELISA) for prothrombin using purified antigen and polyclonal anti-prethrombin-1 IgG. Three different quality control plasmas had coefficients of variation (CV) of 6.5%, 4.9%, and 4.8%. Analytical recovery averaged 103.8%. Results from the ELISA correlated well with factor lie results (r = 0.75). The 5th-95th percentile range for healthy men (n = 10) and women (n = 16) was 97.7 μg/mI to 161.8 μg/ml. The assay exhibited no significant cross-reactivity with other vitamin-K-dependent proteins. Prothrombin showed no diurnal variation. In a study of biovariability the analytical variability, CVA, was 3.1%; the within-subject variability, CVI, was 7.3%; the between-subject variability, CVG, was 14.5%. The critical difference for sequential values (i.e. the smallest percentage change unlikely to be due to CVA or CVI) significant at P = 0.05 was 21.9%. The index of individuality, CVI/CVG, was 0.50. On the basis of the overall biovariability data, primarily the index of individuality, prothrombin as measured in our ELISA is well suited for applications in population-based research. © 1998 Lippincott Williams & Wilkins, Inc.