Comparative evaluation of five different methods for the measurement of plasma factor II levels in carriers of the 20210A prothrombin variant.
The common genetic G to A variation of the prothrombin gene is associated with elevated levels of prothrombin [factor II (FII)] and is recognized as a risk factor for thrombosis. To determine whether one type of assay for plasma FII measurement was more efficient than other assays in displaying high FII levels in 20210A carriers, we compared five methods of measuring FII levels [i.e. an enzyme-linked immunosorbent assay (ELISA), a standard clotting assay, and three chromogenic methods using three different activators: Ecarin, Oxyuranus, and Textarin] in 30 G20210A patients and 30 G20210G controls. Plasma concentrations of factor X and factor VII + factor X were also determined by a clotting procedure. Functional assays were found to be equally efficient in demonstrating significantly higher FII levels in 20210A carriers than in non-carriers (P < 0.0001). With ELISA, the difference observed was less significant (P < 0.005). The specificity of every assay increased with FII cut-off levels; when a cut-off of 115% was applied, sensitivities of functional assays were between 73 and 93%, while sensitivities of ELISA declined dramatically to 33%. FII/factor X and FII/factor VII + factor X ratios were significantly higher in 20210A carriers (P < 0.0001). In conclusion, functional assays are preferentially required for measurements of FII levels in carriers of the 20210A variant.
Laboratory of Hematology, Trousseau Hospital, Tours Cedex, France.
B
B
Delahousse
M
M
Gilbert
F
F
Nicham
C
C
Thirion
B
B
Giraudeau
Y
Y
Gruel
D020413:3' Untranslated Regions / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019540:Area Under Curve; D001780:Blood Coagulation Tests; D002648:Child; D002675:Child, Preschool; D002863:Chromogenic Compounds; D004546:Elapid Venoms / Q000494:pharmacology; D010450:Endopeptidases / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D005167:Factor VII / Q000032:analysis; D005170:Factor X / Q000032:analysis; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D011516:Prothrombin / Q000032:analysis* / Q000235:genetics; D012372:ROC Curve; D012680:Sensitivity and Specificity; D012697:Serine Endopeptidases / Q000494:pharmacology; D019851:Thrombophilia / Q000097:blood / Q000235:genetics*
D020413:3' Untranslated Regions; D002863:Chromogenic Compounds; D004546:Elapid Venoms; C037525:textilotoxin; D005167:Factor VII; D011516:Prothrombin; D005170:Factor X; D010450:Endopeptidases; D012697:Serine Endopeptidases; C051692:scutelarin; C020097:ecarin