Development of a novel, rapid assay for detection of heparin-binding defect antithrombin deficiencies: the heparin-antithrombin binding (HAB) ratio. Issue 1 (January 2015)

• Record Type: Journal Article
• Authors: Moore, Gary W.; de Jager, Naomi; Cutler, Jacqueline A.
• Is Part Of: Thrombosis research. Volume 135:Issue 1(2015)
• Page Start: 161
• Page End: 166
• Publication Date: 2015-01
• Subjects: Thrombosis -- Periodicals; 616.135
• DOI: 10.1016/j.thromres.2014.10.023
• Languages: English
• ISSNs: 0049-3848

Abstract

<abstract abstract-type="author" id="ab0005"> <title id="st0005">Abstract</title> <sec> <title id="st0010">Introduction</title> <p id="sp0005">Qualitative and quantitative antithrombin deficiency predisposes to thrombosis, although patients with heparin-binding dysfunction have a lower incidence than other sub-types. Assays discriminating between qualitative sub-types are not widely available.</p> </sec> <sec> <title id="st1015">Patients/Methods</title> <p id="sp0015">Extended heparin incubation in antithrombin activity assays can overestimate levels in patients with HBDs. Plasmas from genetically proven HBD patients were assayed for antithrombin activity by factor Xa-inhibition and thrombin-inhibition at varying incubation times. Optimal pairings were assessed for generating a quantifiable discrepancy in HBDs by deriving a ratio between results from short and prolonged heparin-incubation assays respectively, the Heparin-antithrombin binding (HAB) ratio. Fourteen patients with hereditary antithrombin deficiency, including five with HBDs, were analysed.</p> </sec> <sec> <title id="st0015">Results</title> <p id="sp0020">The FXa-inhibition assay with 30s and 300 s incubations clearly identified a heterozygous p.Pro73Leu and homozygous p.Leu131Phe, giving HAB ratios of 0.24 and 0.67 respectively (reference range 0.90 – 1.01). However, three plasmas containing mutations with markedly reduced or absent heparin affinity (p.Lys146Glu, p.Gln150Pro, p.Arg79Cys) gave normal results. Nine antithrombin deficient plasmas were tested with the thrombin-inhibition assay and all generated reduced HAB ratios whilst two normal donors did not. The three available HBD plasmas generated lower values than non-HBD plasmas. The mildly reduced HAB ratios in non-HBD deficiencies may have been due to heparin cofactor II reacting with bovine thrombin during extended incubation.</p> </sec> <sec> <title id="st0020">Conclusions</title> <p id="sp0025">HAB ratio from FXa-inhibition assays distinguishes some but not all HBD from non-HBD antithrombins, and thrombin-inhibition assays may be diagnostically applicable with sub-type specific cut-offs.</p> </sec> </abstract>