Abstract Number: PB0586
Meeting: ISTH 2020 Congress
Background: Plasma levels of heparin (UFH) and low molecular weight heparin (LMWH) can be monitored by anti-factor Xa assays relative to commercial calibrators. Unitage of these calibration plasmas are claimed to be traceable to the International Standard (IS). Universal heparin calibrators (unicalibrators) with same labelled potencies for UFH and LMWH are available from several manufacturers and are recommended for use to measure both UFH and LMWH.
Aims: The aim of this study was to determine the traceability and accuracy of these unicalibrators relative to the IS.
Methods: The individual calibrator plasma in unicalibrator sets from three different manufacturers were tested against the ISs for UFH and LMWH using an anti-Xa parallel line bioassay. The potency for each plasma calibrator was estimated and the recovery against quoted values were calculated.
Results: Each spiked calibrator plasma tested validly against both the UFH and the LMWH IS. In all cases the potency estimates against the UFH IS gave higher values than against the LMWH IS (figure 1). Recovery of spiked heparin in all calibration plasmas, irrespective of manufacturer, gave a higher value when assayed against the UFH IS, ranging from 120% (Manufacturer C, Cal 5) to 170% (Manufacturer B, Cal 2) of the labelled values (figure 2). Recovery against the LMWH was good for both manufacturer A, 99% and 100% and manufacturer C, 90 to 107% but was higher for manufacturer B, 103 to 133%.
Conclusions: The traceability and accuracy of all calibration plasmas tested was found to be poor against the UFH IS, values were at least 20% higher than labelled unitage. Whilst there was good agreement against the LMWH IS for the spiked plasmas from manufacturers A and C, there was poor agreement in values for calibrators from manufacturer B. Current commercial unicalibrators are not suitable for estimation of UFH in patient plasmas.
[Figure 1: Potency by parallel line bioassay against either the IS for UFH or for LMWH of each calibrator in a manufacturers’ calibrator set]
To cite this abstract in AMA style:Hogwood J, Gray E. Accuracy of Commercial Universal Calibrators for Measurement of Heparin and Low Molecular Weight Heparin [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/accuracy-of-commercial-universal-calibrators-for-measurement-of-heparin-and-low-molecular-weight-heparin/. Accessed November 26, 2020.
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