Calibration of Local Systems with Lyophilized Calibrant Plasmas Improves the Interlaboratory Variability of the INR in the Italian External Quality Assessment Scheme

Veena Chantarangkul; Armando Tripodi; Bruno M. Cesana; Pier Mannuccio Mannucci

doi:10.1055/s-0037-1614889

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 1999; 82(06): 1621-1626
DOI: 10.1055/s-0037-1614889

Rapid Communication

Schattauer GmbH

Calibration of Local Systems with Lyophilized Calibrant Plasmas Improves the Interlaboratory Variability of the INR in the Italian External Quality Assessment Scheme

Authors

Veena Chantarangkul

²From the Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department of Internal Medicine, University and the Epidemiology Unit, IRCCS Maggiore Hospital, Milano, Italy
Armando Tripodi

²From the Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department of Internal Medicine, University and the Epidemiology Unit, IRCCS Maggiore Hospital, Milano, Italy
Bruno M. Cesana

¹Epidemiology Unit, IRCCS Maggiore Hospital, Milano, Italy
Pier Mannuccio Mannucci

²From the Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Department of Internal Medicine, University and the Epidemiology Unit, IRCCS Maggiore Hospital, Milano, Italy

Abstract

Summary

Calibration with lyophilized calibrant plasmas certified in terms of PT with International Reference Preparations for thromboplastin has been proposed to minimize the effect of coagulometers on the INR. Aim of this study was to test the ability of local calibration with lyophilized calibrant plasmas, combined with a modified statistical approach, to improve the interlaboratory variability of the INR measured on two test plasmas (one coumarin and one artificially-depleted) by participants in the External Quality Assessment Scheme (EQAS). Sets of lyophilized calibrant and test plasmas were sent to the participants in the EQAS, who were asked to determine PT with their own reagent/ instrument combination (local system). Results were returned as PT together with information on the type of local system, the stated International Sensitivity Index (ISI) and the geometric mean of PTs determined by testing with the local system fresh plasmas from 20 healthy subjects. Ninety-two participants using 9 and 11 brands of reagents and instruments returned results. The CV of the INR determined with the stated ISI for the coumarin (Mean INR = 4.39) and artificially-depleted (Mean INR = 4.23) test plasmas were 11.2% and 10.3% and were reduced on the average by 34% and 54%, respectively, when the INR was calculated with the local ISI.

In conclusions, results from this field study involving laboratories and testing systems representative of the real situation in oral anticoagulant monitoring in our country, indicate that local calibration by artificially-depleted plasmas, combined with the proposed statistical approach, is suitable to improve the interlaboratory agreement on the INR.

Key Words

INR - standardization - anticoagulant therapy - lyophilized plasmas

Full Text

References

References
1 Poller L, Triplett DA, Hirsh J, Carroll J, Clarke K. The value of plasma calibrants in correcting coagulometer effect on International Normalized Ratios. An international multicenter study. Am J Clin Path 1995; 103: 358-65.
2 Houbouyan L, Gouguel AF. Long term French experience in INR standardization by a procedure using plasma calibrants. Am J Clin Path 1997; 108: 83-9.
3 Tripodi A, Chantarangkul V, Manotti C, Poggi M, Braga M, Akkawat B, Bucciarelli P, Mannucci PM. A simplified procedure for thromboplastin calibration. The usefulness of lyophilized plasmas assessed in a collaborative study. Thromb Haemost 1996; 75: 309-12.
4 van den Besselaar AMHP. Comparison of lyophilized plasmas with fresh plasmas for calibration of thromboplastin reagents in oral anticoagulant control. Br J Haematol 1996; 93: 437-444.
5 Poller L, van den Besselaar AMHP, Jespersen J, Tripodi A, Houghton D. A comparison of artificially-depleted, lyophilized coumarin and fresh plasmas in thromboplastin calibration. Br J Haematol 1998; 101: 462-7.
6 Poller L, Barrowcliffe TW, van den Besselaar AMHP, Jespersen J, Tripodi A, Houghton D. European Concerted Action on Anticoagulation (ECAA). The multicentre calibration of rabbit and human ECAA Reference Thromboplastins. Thromb Haemost 1996; 76: 977-82.
7 van den Besselaar AMHP. Multicenter calibration of the third BCR Reference Material for thromboplastin, rabbit, plain, coded CRM 149S. Thromb Haemost 1995; 74: 1465-7.
8 WHO Expert Committee on Biological Standardization. Guidelines for thromboplastins and plasma used to control oral anticoagulant therapy. Technical Report Series No. 889. 1999
9 Tomenson JA. A statistician’s independent evaluation. In: van den Besselaar AMHP, Gralnick HR, Lewis SM. (Eds). Thromboplastin calibration and oral anticoagulant control. Martinus Nijhoff Publishers; Boston: 1984: 87-108.
10 Reijnierse GLA, van den Besselaar AMHP, Hermans J. Een nieuw verwer-kingsprogramma van ingezonden uitslagen in het kader van externe kwaliteitsbewaking. Evaringen in 1988. Tijdschr NVKC 1989; 14: 122-7.
11 Johnston M, Brigden M. A cross Canada survey of prothrombin time testing. Does the establishment of local ISI values improve accuracy of INR reporting?. Am J Clin Pathol 1998; 110: 683-90.
12 Brien WF, Baskerville JC, Taberner DA, Crawford L. Calculation vs. calibration for INR determination. Results of inter-laboratory proficiency scheme. Am J Clin Pathol 1999; 111: 193-201.
13 Kitchen S, Jennings I, Woods TAL, Preston FE. Local calibration of INR improves between laboratory agreement: Results from the UK National Quality Assessment Scheme. Thromb Haemost 1999; 81: 60-5.
14 Stevenson KJ, Craig S, Dufty JMK, Taberner DA. System ISI calibration: a universally applicable scheme is possible only when coumarin plasma calibrants are used. Br J Haematol 1997; 96: 435-41.
15 Poller L, van den Besselaar AMHP, Jespersen J, Tripodi A, Houghton D. The importance of “like-to-like” calibrations with freeze-dried plasmas. J Clin Pathol 1998; 51: 275-9.
16 van den Besselaar AMHP. Field study of lyophilized plasmas for local prothrombin time calibration in the Netherlands. J Clin Path 1997; 50: 371-4.
17 Hubbard AR, Margetts SML, Barrowcliffe TW. INR determination using calibrated reference plasmas. Br J Haematol 1997; 98: 74-8.
18 van den Besselaar AMHP, Houbouyan-Reveillard LL, Aillaud MF, Denson KWE, Droullé C, Johnston M, Kitchen S, Lindahl TL, Marren M, Martinuzzo ME, Tripodi A, Vergnes C. Multicenter evaluation of lyophilized and deep-frozen plasmas for assignment of the International Normalized Ratio. Thromb Haemost 1999; 82: 1451-5.
19 Kirkwood TBL. Calibration of reference thromboplastins and standardization of the prothrombin time ratio. Thromb Haemost 1983; 49: 238-44.
20 Poller L, van den Besselaar AMHP, Jespersen J, Tripodi A, Houghton D. Correction for lack of coincidence of normal and abnormal calibration slopes in ISI Determination. Thromb Haemost 1999; 81: 935-9.