title: Effects of pre-analytical variables on the anti-activated factor X chromogenic assay when monitoring unfractionated heparin and low molecular weight heparin anticoagulation.
abstract: The purpose of this study was to determine whether the anti-activated factor X (anti-FXa) assay is less affected by pre-analytical variables in monitoring patients on unfractionated heparin (UFH) and low molecular weight heparin (LMWH) than the activated partial thromboplastin time (aPTT). Forty-six subjects receiving either enoxaparin (LMWH) or UFH were randomly selected. Each study subject had six vacutainer tubes (3.8% sodium citrate, 3.2% sodium citrate) drawn by an atraumatic venipuncture. One tube from each set had a blood to anticoagulant ratio of 9: 1. The other tube had an intentional "short-draw" of approximately 6: 1 blood to anticoagulant ratio. All specimens had an aPTT and a chromogenic anti-FXa assay performed on each specimen regardless of heparin type. The aPTT assay mean with the 3.8% sodium citrate tube short-draw tube was statistically different from the other aPTT assays (P = 0.06). However, all six of the mean anti-FXa assays for the UFH and LMWH heparin subjects were not statistically or clinically different (analysis of variance, P = 0.9878 for UFH and P = 0.9060 for LMWH). The intentional short-draw tube did not affect the anti-FXa assay regardless of the anticoagulant. The anti-FXa assay appears to be a better method for monitoring heparin subjects than the aPTT due to the lack of effect of pre-analytical variables.
authors.affiliation: 59th Clinical Research Squadron, Wilford Hall Medical Center, 2200 Berquist Drive, Lackland AFB, TX 78236-5300, USA. david.mcglasson@lackland af.mil
authors.forename: David L
authors.initials: DL
authors.lastname: McGlasson
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Kaczor
authors.forename: Richard A
authors.initials: RA
authors.lastname: Krasuski
authors.forename: Charles L
authors.initials: CL
authors.lastname: Campbell
authors.forename: Maria R
authors.initials: MR
authors.lastname: Kostur
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Adinaro
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage*; D001780:Blood Coagulation Tests; D002863:Chromogenic Compounds / Q000737:chemistry; D016903:Drug Monitoring; D017984:Enoxaparin / Q000008:administration & dosage; D005170:Factor X / Q000032:analysis* / Q000037:antagonists & inhibitors; D005260:Female; D006493:Heparin / Q000008:administration & dosage*; D006495:Heparin, Low-Molecular-Weight / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time / Q000379:methods
chemical_list: D000925:Anticoagulants; D002863:Chromogenic Compounds; D017984:Enoxaparin; D006495:Heparin, Low-Molecular-Weight; D005170:Factor X; D006493:Heparin