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An international collaborative study on the INR calibration of freeze‐dried reference plasmas
Author(s) -
HUBBARD ANTHONY R.,
MARGETTS SARAH M. L.,
WELLER LYNNE J.,
MACNAB JO,
BARROWCLIFFE TREVOR W.
Publication year - 1999
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1046/j.1365-2141.1999.01225.x
Subject(s) - prothrombin time , reagent , thromboplastin , human plasma , medicine , chromatography , chemistry , surgery , coagulation
A study was carried out to calibrate potential European Reference Plasmas for prothrombin time (PT) standardization. The International Normalized Ratio (INR) values of three freeze‐dried candidate plasmas (one pooled normal and two pools from anticoagulated patients) were determined in 20 laboratories using six thromboplastin reagents comprising three International Reference Thromboplastins (human, rabbit and bovine), two recombinant human reagents and one placental human reagent. Inter‐laboratory variability of INR estimation was low with geometric coefficients of variation (gcv) <10% except in one case. Significant differences in mean INR were found between the different thromboplastins with lowest INR values found with the bovine reagent. INR values from the International rabbit and human reagents differed by <6% and were combined to give proposed assigned INR values. Significant differences in INR estimates from four thromboplastins of human origin may indicate that single assigned INR values are not applicable for use with all thromboplastin reagents. Field trials to assess the validity of single assigned INR values in clinical practice are required.