Thrombin activatable fibrinolysis inhibitor (TAFI) antigen levels exhibit a large interindividual variability in which genetic control seems to play a major role. However, recent reports have questioned the association between TAFI concentration and genotype, suggesting that variable antibody reactivity towards TAFI isoforms, particularly the Thr325Ile polymorphism (1040C/T), may lead to artefacts in TAFI antigen levels. In order to compare assay outcome we determined plasma TAFI levels in 92 healthy individuals, using an enzyme-linked immunosorbent assay (ELISA) (commercial antibodies), an electroimmunoassay (in-house antibodies) and a commercial chromogenic assay (Actichrome® TAFI). Each individual was genotyped for the -438A/G and 1040C/T polymorphisms in the TAFI gene. TAFI levels were significantly associated with genotype in both antigen and chromogenic assays. All assays displayed significant correlations with each other. Linear regression and Bland-Altman agreement analysis in the genotype subgroups showed that neither the genotype nor the concentration affected the relationship between the Actichrome® TAFI and the electroimmunoassay. In contrast, the ELISA/Actichrome® TAFI and the ELISA/electroimmunoassay relationships were concentration- and genotype-dependent. Our results demonstrate that artefacts may arise when measuring TAFI antigen levels by ELISA. Nevertheless, the electroimmunoassay and the Actichrome® TAFI assay support a genotype-related variation of TAFI concentration.

Assay methods, Fibrinolysis, Genetic polymorphisms, Healthy individuals, Thrombin activatable fibrinolysis inhibitor,
British Journal of Haematology
Department of Hematology

Guimarães, A.H.C, van Tilburg, N.H, Vos, H.L, Bertina, R.M, & Rijken, D.C. (2004). Association between thrombin activatable fibrinolysis inhibitor genotype and levels in plasma: Comparison of different assays. British Journal of Haematology, 124(5), 659–665. doi:10.1111/j.1365-2141.2004.04824.x