Accessible Requires Authentication Published by De Gruyter September 10, 2010

Qualitative detection of the Marburg I alloenzyme of factor VII-activating protease by an immunoassay and its comparison to PCR testing

Herbert Schwarz, Sina Stephan, Johannes J. Sidelmann, Bodo Fischer, Harald Althaus, Martin Hahn, Andreas Kappel, Matthias Ehm and Frank Vitzthum


Background: The Marburg I (MRI) single nucleotide poly-morphism (SNP) of the factor VII-activating protease (FSAP) gene has been associated with thrombophilia, thromboembolism, atherosclerosis, and the incidence and progression of carotid stenosis. At present, MRI SNP testing is mainly performed using costly nucleic acid analysis. The ratio between FSAP activity and antigen concentrations in citrated plasma has been used to assess the FSAP genotype.

Methods: This article describes the development of a prototype ELISA for the detection of the MRI FSAP alloenzyme, and its correlation to FSAP genotypes to assess whether a positive MRI FSAP ELISA result may be used as a surrogate marker for the presence of the MRI SNP.

Results: ELISA results were correlated with FSAP genotypes from 523 blood donors measured using PCR. Diagnostic sensitivity and specificity of the assay for determina-tion of the genotype were 100% (95% confidence interval [CI]: 93.36–100) and 99.79% (95% CI: 98.80–99.96), respectively. Maximum run-to-run, within-run, and total coefficients of variation were 7.8%, 7.9%, and 9.9%, respectively. No cross-reactivities with homologues of the MRI FSAP alloenzyme were observed. Test performance was not affected by typical interfering compounds.

Conclusions: The data demonstrate that an immunoassay applying antibodies specific to the MRI FSAP alloenzyme can provide sufficiently accurate detection of the MRI SNP. This will significantly simplify MRI FSAP testing, particularly in large cohorts.

Clin Chem Lab Med 2010;48:1745–9.

Corresponding author: Frank Vitzthum, Siemens Healthcare Diagnostics Products GmbH, Pre-Development, Emil-von-Behring-Str. 76, D-35001 Marburg, Germany Fax: +49 6421 39 3144,

Received: 2010-4-23
Accepted: 2010-6-3
Published Online: 2010-09-10
Published in Print: 2010-12-01

©2010 by Walter de Gruyter Berlin New York