Brien W F, Baskerville J C, Taberner D A, Crawford L
Division of Laboratory Hematology, St Joseph's Health Centre of London, Ontario, Canada.
Am J Clin Pathol. 1999 Feb;111(2):193-201. doi: 10.1093/ajcp/111.2.193.
We surveyed 271 laboratories participating in a quality assessment program to ascertain whether the use of a calibration curve for determining the international normalized ratio (INR) would improve interlaboratory accuracy and precision. Lyophilized warfarinized samples with INR values assigned through manual calibration against internationally assigned rabbit reference thromboplasts were assayed for prothrombin time. Calibration analysis on the results was performed by linear regression. In all but 1 sample, the mean INR value computed by the calibration method was closer to the "true" value than the mean for the conventional calculation method using the International Sensitivity Index (ISI); the ISI calculation consistently overestimated the true value. Interlaboratory variation decreased using the calibration method. Variation from reagent to reagent was greater than from instrument to instrument, but was reduced by the calibration method. The specificity of the ISI for instrument type did not seem to alter the findings. Use of in-house calibrators to verify the ISI improved precision but not necessarily accuracy. The formation of a stable calibration line is consistent over time, but further studies are required to confirm whether such calibration improves the accuracy and precision of INR determination in practice.
我们对参与质量评估项目的271个实验室进行了调查，以确定使用校准曲线测定国际标准化比值（INR）是否会提高实验室间的准确性和精密度。采用通过与国际指定的兔参考凝血活酶进行手动校准而赋予INR值的冻干华法林化样本检测凝血酶原时间。对结果进行校准分析采用线性回归。除1个样本外，在校准方法计算的平均INR值比使用国际敏感指数（ISI）的传统计算方法的平均值更接近“真实”值；ISI计算始终高估真实值。使用校准方法可减少实验室间的差异。不同试剂之间的差异大于不同仪器之间的差异，但校准方法可降低这种差异。ISI对仪器类型的特异性似乎并未改变研究结果。使用内部校准物验证ISI可提高精密度，但不一定能提高准确性。稳定校准线的形成随时间保持一致，但需要进一步研究来证实这种校准在实际中是否能提高INR测定的准确性和精密度。
