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.

Determination of rivaroxaban by different factor Xa specific chromogenic substrate assays: reduction of interassay variability

“…Clot-based methods such as prothrombin time assays and factor Xa chromogenic substrate assays appear to be the most reliable tools. Coagulation assays are inexpensive and easy to perform, but in contrast to chromogenic assays [15] they are affected by coagulation factor abnormalities [16, 17] or levels of plasma proteins [15]. …”

A feasibility study prior to an international multicentre paediatric study to assess pharmacokinetic/pharmacodynamic sampling and sample preparation procedures, logistics and bioanalysis

“…The quality of pre-analytical procedures such as blood sampling as well as sample preparation and transport can considerably affect the results of bioanalytical determinations. This has been reported for electrolytes [ 1 ], metabolomics [ 2 , 3 ], protein markers [ 4 ] and drugs [ [5] , [6] , [7] ]. Especially in clinical trials, study outcomes might be biased without adequately controlled quality of the pre-analytical procedures [ 2 , 8 ], which cannot be compensated by highly sophisticated and validated methods of determination [ 2 ].…”

Usefulness of Cumulative Summation of Differences Method for Determining APTT Reagent Suitability

“…11 Noticeable effects of preanalytical variables on APTT test results were identified in a study by McGlasson et al Also determined by this study, when the APTT test is used for heparin management, inappropriate treatment may occur creating the potential for life threatening complications. 12 Due to variances in APTT reagents it has also been identified in a study performed by Eiklboom & Hirsh that laboratories may have difficulty providing an accurate test range used for treatment and monitoring of heparin therapy, creating difficulty for clinicians to treat patients effectively. 13 In order to determine if the acceptability range of 7 sec.…”