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Determination of APTT factor sensitivity - the misguiding guideline.

Lawrie, AS; Kitchen, S; Efthymiou, M; Mackie, IJ; Machin, SJ; (2013) Determination of APTT factor sensitivity - the misguiding guideline. Int J Lab Hematol , 35 (6) pp. 652-657. 10.1111/ijlh.12109. Green open access

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Abstract

INTRODUCTION: The Clinical and Laboratory Standards Institute (CLSI) has produced a guideline detailing how to determine the activated partial thromboplastin time's (APTT) sensitivity to clotting factor deficiencies, by mixing normal and deficient plasmas. Using the guideline, we determined the factor sensitivity of two APTT reagents. METHODS: APTTs were performed using Actin FS and Actin FSL on a Sysmex CS-5100 analyser. The quality of factor-deficient and reference plasmas from three commercial sources was assessed by assaying each of the clotting factors within the plasmas and by performing thrombin generation tests (TGT). RESULTS: Testing samples from 50 normal healthy subjects gave a two-standard deviation range of 21.8-29.2 s for Actin FS and 23.5-29.3 s for Actin FSL. The upper limits of these ranges were subsequently used to determine APTT factor sensitivity. Assay of factor levels within the deficient plasmas demonstrated that they were specifically deficient in a single factor, with most other factors in the range 50-150 iu/dL (Technoclone factor VII-deficient plasma has 26 iu/dL factor IX). APTTs performed on mixtures of normal and deficient plasmas gave diverse sensitivity to factor deficiencies dependent on the sources of deficient plasma. TGT studies on the deficient plasmas revealed that the potential to generate thrombin was not solely associated with the levels of their component clotting factors. CONCLUSION: Determination of APTT factor sensitivity in accordance with the CLSI guideline can give inconsistent and misleading results.

Type: Article
Title: Determination of APTT factor sensitivity - the misguiding guideline.
Open access status: An open access version is available from UCL Discovery
DOI: 10.1111/ijlh.12109
Publisher version: http://dx.doi.org/10.1111/ijlh.12109
Additional information: © 2013 The Authors. International Journal of Laboratory Hematology Published by John Wiley & Sons Ltd. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Keywords: APTT ; plasma clotting factors;
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Cancer Institute
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Cancer Institute > Research Department of Haematology
URI: http://discovery.ucl.ac.uk/id/eprint/1395051
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