title: Comparison of the anticoagulant response of a novel fluorogenic anti-FXa assay with two commercial anti-FXa chromogenic assays.
abstract: BACKGROUND
  Fast and accurate monitoring is crucial in the successful regulation of coagulation therapy. For the treatment of venous thromboembolism, both unfractionated heparin (UFH) and low molecular weight heparins (LMWHs) are commonly administered. The chromogenic anti-factor Xa (FXa) assay is currently considered the 'gold standard' assay for monitoring LMWH. However different commercial chromogenic methods often differ when tested with the same samples. Fluorogenic anti-FXa assays have the potential to offer greater benefits over chromogenic assays in terms of greater specificity, sensitivity and they are not so influenced by sample opacity or turbidity.
  
  
  METHODS
  Commercial plasmas were spiked with pharmacologically relevant concentrations (0-1 U/ml) of UFH, enoxaparin, and tinzaparin. The fluorogenic assay was carried out using previously optimized concentrations of 12 nM FXa and 2.7μM fluorogenic substrate, in addition to 6μl of 100mM CaCl(2) and 44μl of plasma. The Biophen® and Coamatic chromogenic assays were carried out according to the manufacturer's instructions. Reaction rates and endpoint values were analyzed and statistical analysis by means of one-way analysis of variance (ANOVA) was performed.
  
  
  RESULTS
  The fluorogenic anti-FXa assay was found to have the broadest therapeutic range of 0-1 U/ml with CVs of<5% for UFH and tinzaparin and CVs<9% for enoxaparin. Despite their limited measuring range, good assay reproducibility was observed with both chromogenic kits.
  
  
  CONCLUSIONS
  This study indicated that the fluorogenic assay is the most sensitive assay with the broadest dynamic range for monitoring LMWH therapy when compared with standard chromogenic assays.
authors.affiliation: Biomedical Diagnostics Institute, National Centre for Sensor Research, Dublin City University, Dublin 9, Ireland.
authors.forename: Leanne F
authors.initials: LF
authors.lastname: Harris
authors.forename: Aoife
authors.initials: A
authors.lastname: O'Brien
authors.forename: Vanessa
authors.initials: V
authors.lastname: Castro-López
authors.forename: James S
authors.initials: JS
authors.lastname: O'Donnell
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Killard
mesh_terms: D000925:Anticoagulants / Q000097:blood / Q000737:chemistry / Q000494:pharmacology; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D017984:Enoxaparin / Q000097:blood; D015951:Factor Xa / Q000737:chemistry / Q000302:isolation & purification; D065427:Factor Xa Inhibitors; D005456:Fluorescent Dyes / Q000737:chemistry; D006493:Heparin / Q000097:blood / Q000737:chemistry / Q000494:pharmacology*; D006495:Heparin, Low-Molecular-Weight / Q000097:blood / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D000078222:Tinzaparin
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D065427:Factor Xa Inhibitors; D005456:Fluorescent Dyes; D006495:Heparin, Low-Molecular-Weight; D000078222:Tinzaparin; D006493:Heparin; D015951:Factor Xa