Community Research and Development Information Service - CORDIS

Abstract

The aim of the present project was to provide an alternative method of estimating INR (International Normalised Ratio) which will lead to increased inter-laboratory agreement and also overcome the need for time-consuming local calibration exercises which are currently required to compensate for differences in instrumentation and reagents. It is proposed to use three freeze-dried pooled plasmas (one normal plasma pool and two abnormal plasma pools with increased INR values) each with an assigned INR value to construct a calibration curve by plotting local prothrombin time (PT) vs. assigned INR value. The INR of test plasmas can then be interpolated from local PT estimates. Three definitive preparations consisting of a pooled normal plasma and two pools of patient plasma (1 medium and 1 high INR range) were prepared for INR calibration in a collaborative study involving 20 laboratories. Estimates of homogeneity (by weight and PT estimation) and stability indicated that the preparations were suitable for use as reference preparations. INR values were estimated using three International Reference Thromboplastin preparations (BCT/253 - human, RBT/90 - rabbit, OBT/79 - bovine). Inter-laboratory variability of INR estimates was lowest with the normal plasma (maximum GCV 4.32%) and highest with the high INR patient plasma (maximum GCV 10.99%). The low variability was the main reason for significant differences between some mean INR estimates with different thromboplastin reagents. The largest difference was seen with abnormal plasma-2 between the INR estimate with OBT/79 (3.20) and the estimates with RBT/90 (3.93) and BCT/253 (3.75) and this invalidated the assignment of a mean INR value calculated from the results obtained with all three thromboplastin reagents. The assigned INR values are the geometric means of the INR estimates obtained by the individual laboratories using BCT/253 and RBT/90. These assigned values are intended to be used with all thromboplastin reagents

Additional information

Authors: BARROWCLIFFE T W, National Institute for Biological Standards and Control, Hertfordshire (GB);HUBBARD A R, National Institute for Biological Standards and Control, Hertfordshire (GB);MARGETTS S, National Institute for Biological Standards and Control, Hertfordshire (GB);WELLER J, National Institute for Biological Standards and Control, Hertfordshire (GB);MACNAB J, National Institute for Biological Standards and Control, Hertfordshire (GB);BENNINK D, European Commission, DG Research, Standards, Measurement and Testing, Brussels (BE);GAWLIK B M, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);KLEIN C L, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE);LAMBERTY A, European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Geel (BE)
Bibliographic Reference: EUR 21060 EN (2004), 41 pp. Free of charge
Availability: Available from European Commission, JRC Knowledge Management Unit, Ispra (IT) Tel: +39 033278 9893 Fax: +39 033278 5409 E-mail: jrc-publications-office@ec.europa.eu or Bruxelles (BE) Tel: +32 2 295 76 24 Fax: +32 2 299 63 22
ISBN: ISBN: 92-894-5172-6
Record Number: 200417512 / Last updated on: 2004-06-01
Category: PUBLICATION
Original language: en
Available languages: en