title: Direct chromogenic substrate immuno-capture activity assay for testing of factor VII-activating protease.
abstract: BACKGROUND
  The Marburg I (MRI) single nucleotide polymorphism (SNP) of the factor VII-activating protease (FSAP) gene has been associated with thrombophilia and atherosclerotic disease. PCR is used to detect the SNP. Also, the specific FSAP activity to cleave single-chain urokinase-type plasminogen activator (scu-PA) serves as a surrogate for PCR testing. Development of further assays is indicated in order to increase testing opportunities for future studies.
  
  
  METHODS
  A direct chromogenic substrate immuno-capture activity assay for FSAP (FSAP dcs activity assay) was established. Performance characteristics of the FSAP dcs activity assay were compared to the FSAP scu-PA activity assay.
  
  
  RESULTS
  The FSAP dcs activity assay detects FSAP activity from 25% to 150% of the norm. Total CVs ranged from 6% to 10% for FSAP wild type samples and 9%-18% for MRI samples. Correlation between the FSAP dcs and scu-PA activity assays was low (R=0.7). The FSAP dcs activity determined the presence of the MRI FSAP alloenzyme with a diagnostic sensitivity and specificity of 100% [95% confidence interval (CI): 89.6%-100%] and 96.2% (95% CI: 93.2%-97.4%), respectively, whereas the specific FSAP dcs activity increased specificity to 99.0% (95% CI: 97.2%-99.6%).
  
  
  CONCLUSIONS
  The specific FSAP dcs activity represents a reliable method for the detection of the FSAP MRI alloenzyme. Due to the limited correlation between the FSAP dcs and scu-PA activity assays, these different measurands may exhibit different utility in research and clinical applications. Thus, the FSAP dcs activity assay can represent a valuable complement or alternative for FSAP testing in future studies.
authors.affiliation: Siemens Healthcare Diagnostics Products GmbH, Marburg, Germany.
authors.forename: Sina
authors.initials: S
authors.lastname: Stephan
authors.forename: Herbert
authors.initials: H
authors.lastname: Schwarz
authors.forename: Anja
authors.initials: A
authors.lastname: Haude-Barten
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: Sidelmann
authors.forename: Bodo
authors.initials: B
authors.lastname: Fischer
authors.forename: Harald
authors.initials: H
authors.lastname: Althaus
authors.forename: Martin
authors.initials: M
authors.lastname: Hahn
authors.forename: Andreas
authors.initials: A
authors.lastname: Kappel
authors.forename: Matthias
authors.initials: M
authors.lastname: Ehm
authors.forename: Frank
authors.initials: F
authors.lastname: Vitzthum
mesh_terms: D000293:Adolescent; D000328:Adult; D002863:Chromogenic Compounds / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism; D057075:Enzyme Assays / Q000379:methods*; D005260:Female; D005838:Genotype; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007527:Isoenzymes / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D008297:Male; D009842:Oligopeptides / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D012697:Serine Endopeptidases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism; D055815:Young Adult
chemical_list: D002863:Chromogenic Compounds; D007527:Isoenzymes; D009842:Oligopeptides; D019343:Citric Acid; C433550:HABP2 protein, human; D012697:Serine Endopeptidases; D014568:Urokinase-Type Plasminogen Activator