PDF herunterladen
Thromb Haemost 1991; 66(04): 442-445
DOI: 10.1055/s-0038-1646435
Review Article
Schattauer GmbH Stuttgart

Determination of the Mean Normal Prothrombin Time for Assessment of International Normalized Ratios

Usefulness of Lyophilized Plasma
R H M Peters
1   The Laboratory for Clinical Chemistry and Haematology, Hospital "Medisch Spectrum Twente", Enschede, The Netherlands
,
A M H P van den Besselaar
2   The Thrombosis and Haemostasis Research Unit, Department of Haematology, University Hospital Leiden, The Netherlands
,
F M F G Olthuis
1   The Laboratory for Clinical Chemistry and Haematology, Hospital "Medisch Spectrum Twente", Enschede, The Netherlands
› Institutsangaben
Weitere Informationen

Publikationsverlauf

Received 27. Dezember 1990

Accepted 03. April 1991

Publikationsdatum:
25. Juli 2018 (online)

Auch verfügbar auf
  als PDF herunterladen  Lizenzen und Reprints

Summary

To report a Prothrombin Time (PT) as International Normalized Ratio in controlling oral anticoagulant therapy, the Mean Normal PT (MNPT) is required. To correct for methodological differences in performing the PT test, each laboratory should determine its own MNPT for each batch of reagent using fresh blood samples from a large number of normal individuals. This would be a laborious procedure. Two models for simplified assessment of MNPT were investigated by two laboratories in a collaborative study. According to the models, the MNPT of a new batch of reagent is calculated, using the PT of a lyophilized control plasma measured with the new batch and a reference batch, as well as the MNPT of the reference batch obtained with fresh samples. Experimental results were obtained with 19 batches of bovine thromboplastin, 4 lyophilized normal control plasmas and fresh blood samples of 40 normal individuals. The PTs of the 4 lyophilized normal control plasmas were not identical to the MNPT of the fresh normal samples and also different from each other. Therefore, the uncorrected PTs of these control plasmas cannot be used as MNPT.

In general, there was good agreement between measured and calculated MNPT, although some control plasmas gave better results than others. There were no significant differences between the results obtained by both calculation models.

 

  • References

  • 1 International Committee for Standardization in Haematology and International Committee on Thrombosis and Haemostasis. ICSH/ICTH recommendations for reporting prothrombin time in oral anti-coagulant control. Thromb Haemostas 1985; 53: 155-6
    PubMedGoogle Scholar
  • 2 WHO Expert Committee on Biological Standardization 33rd Report WHO. Techn Rep Ser 1983; 687: 81-105
    PubMedGoogle Scholar
  • 3 Kirkwood TBL. Calibration of reference thromboplastins and standardization of the prothrombin time ratio. Thromb Haemostas 1983; 49: 238-44
    PubMedGoogle Scholar
  • 4 Van den Besselaar AMHP. Standardization of the prothrombin time in oral anticoagulant control. Haemostasis 1985; 15: 271-7
    PubMedGoogle Scholar
  • 5 Peters RHM, van den Besselaar AMHP, Olthuis FMFG. A multicentre study to evaluate the method dependency of the International Sensitivity Index of bovine thromboplastin. Thromb Haemostas 1989; 61: 166-9
    PubMedGoogle Scholar
  • 6 Poller L, Hirsh J. A simple system for the derivation of International Normalized Ratios for the reporting of prothrombin time results with North American thromboplastin reagents. Am J Clin Pathol 1989; 92: 124-6
    CrossrefPubMedGoogle Scholar
  • 7 Hermans J, van den Besselaar AMHP, Loeliger EA, van de Velde EA. A collaborative calibration study of reference materials for thromboplastins. Thromb Haemostas 1983; 50: 712-7
    PubMedGoogle Scholar
  • 8 Cornbleet PJ, Gochman N. Incorrect least-square regression coefficients in method-comparison analysis. Clin Chem 1979; 25: 432-8
    PubMedGoogle Scholar