The Effect of Some Instruments for Prothrombin Time Testing on the International Sensitivity Index (ISI) of Two Rabbit Tissue Thromboplastin Reagents

Marina Poggio; Antonius M H P van den Besselaar; Edo A van der Velde; Rogier M Bertina

doi:10.1055/s-0038-1651019

Thrombosis and Haemostasis, Table of Contents

Thromb Haemost 1989; 62(03): 868-874
DOI: 10.1055/s-0038-1651019

Original Article

Schattauer GmbH Stuttgart

The Effect of Some Instruments for Prothrombin Time Testing on the International Sensitivity Index (ISI) of Two Rabbit Tissue Thromboplastin Reagents

Marina Poggio

The Thrombosis and Hemostasis Research Unit, Department of Haematology, University Hospital of Leiden, and Department of Medical Statistics, University of Leiden, The Netherlands

,

Antonius M H P van den Besselaar

The Thrombosis and Hemostasis Research Unit, Department of Haematology, University Hospital of Leiden, and Department of Medical Statistics, University of Leiden, The Netherlands

,

Edo A van der Velde

The Thrombosis and Hemostasis Research Unit, Department of Haematology, University Hospital of Leiden, and Department of Medical Statistics, University of Leiden, The Netherlands

,

Rogier M Bertina

The Thrombosis and Hemostasis Research Unit, Department of Haematology, University Hospital of Leiden, and Department of Medical Statistics, University of Leiden, The Netherlands

› Author Affiliations

Abstract

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Summary

Two commercial rabbit tissue thromboplastins were calibrated against the International Reference Preparation for rabbit thromboplastin (coded RBT/79) by one laboratory using the manual technique, a semi-automatic electro-mechanical coagulometer and three different automatic photo-optical instruments. The calibration of the two reagents was performed in three and two different exercises, respectively, and showed good reproducibility of the procedure. The purpose of calibration is providing a formula for the assessment of the International Normalized Ratio (INR) for patients receiving oral anticoagulants. The World Health Organization (WHO) model for thromboplastin calibration leads to the equation INR = R^ISI, in which R is the prothrombin time ratio and ISI the International Sensitivity Index of the calibrated thromboplastin/instrument system. This equation was adequate for one reagent, but not for the other when it was used in combination with the four instruments. At therapeutic intensities of anticoagulation, the deviation from the WHO-model observed for the second reagent was clinically insignificant. The WHO model was fully adequate when the second reagent was used with the manual technique. For both thromboplastins, there were statistically significant differences in ISI between the four instruments. The largest difference-amounting to approximately 10%-was observed between two photo-optical instruments. The order of instruments with increasing ISI was the same for the two reagents. It is recommended that thromboplastin manufacturers specify the instruments used for calibration of their reagent.

Keywords

Oral anticoagulant control - Prothrombin time - Thromboplastin calibration - International Sensitivity Index - Instrument effect

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References

References
1 Lam-Po-Tang PR L C, Poller L. Oral anticoagulant therapy and its control: an international survey. Thromb Diath Haemorrh 1975; 34: 419-425
2 ICTH/ICSH. Prothrombin time standardization: Report of the Expert Panel on Oral Anticoagulant Control. Thromb Haemostas 1979; 42: 1073-1114
3 Zucker S, Brosious E, Cooper GR. One stage prothrombin time survey. Am J Clin Pathol 1970; 53: 340-347
4 Loeliger EA. ICSH/ICTH recommendations for reporting prothrombin time in oral anticoagulant control. Thromb Haemostas 1985; 53: 155-156
5 Loeliger EA, Poller L, Samama M, Thomson JM, Van den Besselaar AM H P, Vermylen J, Verstraete M. Questions and answers on prothrombin time standardisation in oral anticoagulant control. Thromb Haemostas 1985; 54: 515-517
6 WHO Expert Committee on Biological Standardization, 33rd Report. Tech Rep Ser 687, WHO, Geneva 1983: 81
7 Kirkwood TB L. Calibration of reference thromboplastins and standardisation of the prothrombin time ratio. Thromb Haemostas 1983; 49: 238-244
8 Palareti G, Coccheri S, Poggi M, Bonetti M, Cervi V, Mazzuca A, Savoia M, Veri L, Fiori F, Gaspari G, Palareti A. Oral anticoagulant therapy control: Evidence that INR expression improves the interlaboratory comparability of results. The Bologna Oral Anticoagulant Control Exercise. Thromb Haemostas 1987; 58: 905-910
9 Hermans J, Van den Besselaar AM H P, Loeliger EA, Van der Velde EA. A collaborative calibration study of reference materials for thromboplastins. Thromb Haemostas 1983; 50: 712-717
10 Van den Besselaar AM H P, Evatt BL, Brogan DR, Triplett DA. Proficiency testing and standardization of prothrombin time: Effect of Thromboplastin, Instrumentation and Plasma. Am J Clin Pathol 1984; 82: 688-699
11 Evatt BL, Brogan D, Triplett D, Koepke J, Waters G. Effect of thromboplastin and instrumentation on the prothrombin time test. Clin Lab Haemat 1981; 3: 331-342
12 Starr H, Rhoades P, Lam-Po-Tang PR, Archer GT. Prothrombin times: An evaluation of four thromboplastins and four machines. Pathology 1980; 12: 567-574
13 Van den Besselaar AM H P. Standardization of prothrombin time in oral anticoagulant control. Haemostasis 1985; 15: 271-277
14 Loeliger EA, Van den Besselaar AM H P, Hermans J, Van der Velde EA. Certification of three reference materials for thromboplastins. Commission of the European Communities, Brussels, 1984. Report EUR 7763 EN.
15 Van der Velde EA. Orthogonal regression equation. In: Thromboplastin Calibration and Oral Anticoagulant Control. Van den Besselaar AM H P, Gralnick HR, Lewis SM. (eds). Martinus Nijhoff; 1984. The Hague: 25-39
16 Thomson JM, Tomenson JA, Poller L. The calibration of the second primary international reference preparation for thromboplastin (thromboplastin, human, plain, coded BCT/253). Thromb Haemostas 1984; 52: 336-342
17 Gogstad GO, Wadt J, Smith P, Brynildsrud T. Utility of a modified Calibration model for reliable conversion of thromboplastin times to International Normalized Ratios. Thromb Haemostas 1986; 56: 178-182
18 Community Bureau of Reference-BCR. Certified Reference Material-Certificate of measurement. BCR No 149, Thromboplastin rabbit (RBT/79). Commission of the European Communities, Brussels 1981
19 Loeliger EA, Van den Besselaar AM H P, Lewis SM. Reability and clinical impact of the normalization of the prothrombin times in oral anticoagulant control. Thromb Haemostas 1985; 53: 148-154
20 Van den Besselaar AM H P, Hermans J, Van der Velde EA, Bussemaker-Verduyn den Boer E, Van Halem-Visser LP, Jansen-Grüter R, Loeliger EA. The calibration of rabbit tissue thromboplastins: experience of the Dutch Reference Laboratory for anticoagulant control. J Biol Standardization 1986; 14: 305-317
21 Poller L, Thomson JM, Taberner DA. Effect of automation on prothrombin time test in NEQAS surveys. J Clin Pathol 1989; 42: 097-100