title: Tests for the measurement of factor VII-activating protease (FSAP) activity and antigen levels in citrated plasma, their correlation to PCR testing, and utility for the detection of the Marburg I-polymorphism of FSAP.
abstract: BACKGROUND
  The single nucleotide Marburg I (MRI) polymorphism of the factor VII-activating protease (FSAP) gene, the prourokinase-activating activity of FSAP, and antigen levels of FSAP in plasma have been associated with incidence and progression of carotid stenosis and venous thromboembolism. However, more information on the extent of these associations, potential further ones, and respective clinical utilities remain to be determined. At present, testing is performed mainly by PCR assays based on probes or SYBR Green I. Some studies include testing for antigen levels of total FSAP and its ability to activate prourokinase. To test large cohorts, it is beneficial to rely on assays that are cost-effective, reliable, easy to use, rapid to perform, and that may eventually be automated. In addition, it appears advantageous to use functional tests or tests that determine antigen levels as they may relate more closely to the phenotype than the genotype does.
  
  
  METHODS
  Tests for the measurements of antigen levels of FSAP and its prourokinase-activating activity were improved and performance characteristics assessed. To determine the FSAP genotypes, an amplification created restriction site (ACRS) PCR test was developed.
  
  
  RESULTS
  Key performance characteristics of the FSAP activity and antigen tests were as follows: measuring range: 350-1400 mPEU/mL and 1.8-120 ng/mL, total coefficients of variation (CV): 5%-20% and 5%-14%, within-run CV: 4%-11% and 2.3%-12%, and run-to-run CV: 2%-17% and 4.3%-8.3%, respectively. The ratio of the activity and antigen level of FSAP correctly identified the FSAP genotypes of 126 samples tested.
  
  
  CONCLUSIONS
  The ACRS PCR test is useful for laboratories that do not have the equipment to perform probe or SYBR Green I based real-time PCR. Furthermore, the tests developed for the determination of FSAP activity and antigen levels are convenient for determining clinical correlations, even for large population studies. The ratio of activity and antigen level of FSAP appears to be a promising and efficient alternative to molecular diagnostic techniques to detect the MRI polymorphism of FSAP.
authors.affiliation: Dade Behring Marburg GmbH, A Siemens Company, 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: Borchert
authors.forename: Delia
authors.initials: D
authors.lastname: Bussfeld
authors.forename: Elfriede
authors.initials: E
authors.lastname: Quak
authors.forename: Beate
authors.initials: B
authors.lastname: Simshaeuser-Knaub
authors.forename: Stefan
authors.initials: S
authors.lastname: Teigelkamp
authors.forename: Fritz
authors.initials: F
authors.lastname: Behrens
authors.forename: Frank
authors.initials: F
authors.lastname: Vitzthum
mesh_terms: D000941:Antigens / Q000097:blood* / Q000378:metabolism; D001774:Blood Chemical Analysis / Q000191:economics / Q000379:methods*; D003365:Costs and Cost Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005838:Genotype; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods*; D011110:Polymorphism, Genetic; D012680:Sensitivity and Specificity; D012697:Serine Endopeptidases / Q000097:blood* / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors
chemical_list: D000941:Antigens; C433550:HABP2 protein, human; D012697:Serine Endopeptidases