STANDARDIZATION OF PROTHROMBIN FRAGMENT 1.2 MEASUREMENT - EFFECTS OF PREANALYTICAL VARIABLES AND CALIBRATOR SELECTION

Background. - Immunoassays for prothrombin fragment 1.2 (F1.2) provide a specific measure of thrombin generation and offer potential value i n detecting activation of the coagulation system and monitoring antico agulant therapy. To standardize laboratory measurements of this analyt e, it is important to define factors affecting interassay variability. Objective. - To determine the potential for standardization of F1.2 m easurement by examining the effects of preanalytical variables and cal ibrator selection on F1.2 measurement. Materials and Methods. - Using three commercially available immunoassays, interassay and intra-assay correlations for F1.2 were determined using blood samples collected in to heparin, citrate, and a solution of ethylenediaminetetraacetic acid , aprotinin,and D-phenylalanyl-L-prolyl-L-arginyl chloromethyl ketone; In a cohort of patients, interassay correlations for F1.2 were determ ined using blood collected from an arterial catheter. Dose-response cu rves were generated for each manufacturer-supplied calibrator set by s ubstitution into each of the previously untested competing immunoassay s. Results. - F1.2 immunoassays with the same recommended specimen ant icoagulant displayed stronger correlation than assays requiring differ ent anticoagulants. Furthermore, a stronger interassay correlation was elicited by samples collected through an intra-arterial catheter as o pposed to venipuncture. F1.2 calibrator sets differed quantitatively, with buffer-related matrix effects contributing to interassay variabil ity. Conclusion. - Analytical standardization of F1.2 immunoassays is possible when a common anticoagulant, blood collection method, and cal ibrator set are used.