title: Variability in plasma prothrombin concentration: implications for use in epidemiology.
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 IIc) 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 IIc results (r=0.75). The 5th-95th percentile range for healthy men (n=10) and women (n=16) was 97.7 pg/ml to 161.8 microg/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, CV(A), was 3.1%; the within-subject variability, CV(I), was 7.3%; the between-subject variability, CV(G), was 14.5%. The critical difference for sequential values (i.e. the smallest percentage change unlikely to be due to CV(A) or CV(I)) significant at P=0.05 was 21.9%. The index of individuality, CV(I)/CV(G), 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.
authors.affiliation: Department of Pathology, University of Vermont, Colchester 05446, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Smiles
authors.forename: E M
authors.initials: EM
authors.lastname: Macy
authors.forename: P A
authors.initials: PA
authors.lastname: Sakkinen
authors.forename: E G
authors.initials: EG
authors.lastname: Bovill
authors.forename: K G
authors.initials: KG
authors.lastname: Mann
authors.forename: R P
authors.initials: RP
authors.lastname: Tracy
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants; D002940:Circadian Rhythm; D019343:Citric Acid; D004492:Edetic Acid; D004797:Enzyme-Linked Immunosorbent Assay; D004813:Epidemiology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G; D008297:Male; D008875:Middle Aged; D017293:Protein S / Q000032:analysis; D011516:Prothrombin / Q000032:analysis*; D011786:Quality Control; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D000925:Anticoagulants; D007074:Immunoglobulin G; D017293:Protein S; D019343:Citric Acid; D011516:Prothrombin; D004492:Edetic Acid