Klin Padiatr 2010; 222(3): 164-167
DOI: 10.1055/s-0030-1251988
Original Article

© Georg Thieme Verlag KG Stuttgart · New York

Conventional Chromogenic Heparin Assays are Influenced by Patient's Endogenous Plasma Antithrombin Levels

Einfluss endogener Antithrombinplasmaspiegel auf die Heparinbestimmung mit chromogenen SubstratenL. G. Mitchell1 , P. Vegh1
  • 1University of Alberta, Pediatrics, Edmonton, Canada
Further Information

Publication History

Publication Date:
31 May 2010 (online)

Abstract

Objectives: To determine, in vitro, the influence of plasma AT concentrations on heparin levels as measured by commercially available chromogenic kits.

Methods: Purified AT was added to plasma that was immune depleted of AT at the following final concentrations: 0, 0.5, 1.0, 1.5, 2.0, 2.5 u/ml. Heparin was added to each of the AT concentrations at the following final concentrations: 0, 0.2, 0.4 u/ml. Heparin levels were then determined using 5 different Anti-Xa (n=4) or Anti-IIa (n=1) commercial kits. All kits provided purified AT to be added to the assay system.

Results: When heparin was added to plasma, heparin concentrations measured were dependent on plasma concentrations of AT (p<0.001). When plasma concentrations of AT were less than 1.0 u/ml heparin concentrations were underestimated and when plasma concentrations of AT were greater than 1.0 u/ml actual heparin levels were over estimated. There was no significant difference in the findings between the various commercial Xa or IIa kits. In the absence of heparin, anticoagulant activity was detected when plasma AT concentrations were above 1.0 u/ml. There was a statistically significant correlation between plasma concentrations of AT and the amount of anticoagulant activity (p<0.001).

Conclusions: Conventional chromogenic heparin assays are influenced by endogenous plasma AT levels.

Zusammenfassung

Hintergrund: Der Einfluss der Plasmaantithrombinkonzentration auf die Heparinspiegel-bestimmung mittels kommerzieller chromogener Substratmethoden soll untersucht werden.

Methoden: Gereinigtes Antithrombin (AT) wurde zu AT-Mangelplasma in den Konzentrationen von 0, 0,5, 1,0, 1,5, 2,0, 2,5 u/ml hinzugegeben. Anschließend wurde zu jeder AT-Konzentration Heparin in den folgenden Konzentrationen zugefügt: 0, 0,2, 0,4 u/ml. Heparinspiegel wurden mit 5 unterschiedlichen kommerziellen Bestimmungsmethoden als Anti-Xa (n=4) oder Anti-IIa (n=1) bestimmt. Alle Kits stellten gereinigtes AT für die Durchführung der Analysen zur Verfügung.

Ergebnisse: Nach Heparinzugabe war die gemessene Heparinkonzentration signifikant abhängig von der Plasma-AT-Konzentration (p<0,001). War die AT-Konzentration <1,0 u/ml, wurde die Heparinkonzentration zu niedrig gemessen, war die Plasma-AT-Konzentration > 1,0u/ml, wurde die Heparinkonzentration zu niedrig gemessen, war die Plasma-AT-Konzentration >1,0 u/ml wurden die Heparinkonzentrationen zu hoch gemessen. Wir konnten keine Unterschiede zwischen den kommerziellen Kit-Anbietern feststellen. In Abwesenheit von Heparin konnte eine unspezifische antikoagulatorische Aktivität bei Plasma-AT-Konzentrationen >1,0 u/ml nachgewiesen werden (p<0,001).

Schlussfolgerung: Chromogene Heparinbestimmungsmethoden sind durch endogene AT Plasmaspiegel beeinflussbar.

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Correspondence

Prof. Lesley G. Mitchell

University of Alberta Pediatrics

11304-89 Avenue

T6G 2C7 Edmonton

Canada

Phone: +1/780/439 9713

Fax: +1/780/492 3350

Email: lesley.mitchell@albertahealthservices.ca

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