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Association between thrombin activatable fibrinolysis inhibitor genotype and levels in plasma: Comparison of different assays

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Author: Guimarães, A.H.C. · Tilburg, N.H. van · Vos, H.L. · Bertina, R.M. · Rijken, D.C.
Source:British Journal of Haematology, 5, 124, 659-665
Identifier: 237657
doi: doi:10.1111/j.1365-2141.2004.04824.x
Keywords: Biomedical Research · Assay methods · Fibrinolysis · Genetic polymorphisms · Healthy individuals · Thrombin activatable fibrinolysis inhibitor · controlled study · correlation analysis · DNA polymorphism · Electroimmunoassay · Enzyme analysis · Enzyme assay · Enzyme blood level · Enzyme linked immunosorbent assay · Intermethod comparison · Linear regression analysis · Adult · Aged · Carboxypeptidase U · Female · Genotype · Humans · Immunoassay · Male · Middle Aged · Polymorphism, Genetic · Regression Analysis


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. © 2004 Blackwell Publishing Ltd. Chemicals / CAS: Carboxypeptidase U, EC