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 in detecting activation of the coagulation system and monitoring anticoagulant therapy. To standardize laboratory measurements of this analyte, it is important to define factors affecting interassay variability.

OBJECTIVE

To determine the potential for standardization of F1.2 measurement by examining the effects of preanalytical variables and calibrator 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 into 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 determined using blood collected from an arterial catheter. Dose-response curves were generated for each manufacturer-supplied calibrator set by substitution into each of the previously untested competing immunoassays.

RESULTS

F1.2 immunoassays with the same recommended specimen anticoagulant displayed stronger correlation than assays requiring different anticoagulants. Furthermore, a stronger interassay correlation was elicited by samples collected through an intra-arterial catheter as opposed to venipuncture. F1.2 calibrator sets differed quantitatively, with buffer-related matrix effects contributing to interassay variability.

CONCLUSION

Analytical standardization of F1.2 immunoassays is possible when a common anticoagulant, blood collection method, and calibrator set are used.