Key result
PT-INR values measured with the INRatio point-of-care device were higher than traditional laboratory measurements, with a mean difference (Lab-INR minus INRatio) of -0.33.
Why the study?
Variability in PT-INR values measured with various point-of-care devices compared with traditional plasma-based laboratory measurement in clinical practice had yet to be clarified.
Does PT-INR measurement by point-of-care devices (INRatio/INRatio 2 and CoaguChek XS) differ from traditional laboratory measurement in patients receiving warfarin?
Cross-Sectional (n=393)
No
Does PT-INR measurement by point-of-care devices (INRatio/INRatio 2 and CoaguChek XS) differ from traditional laboratory measurement in patients receiving warfarin?
Mean Difference: -0.33 (95% CI -0.35–-0.31)
PT-INR values measured by the INRatio point-of-care device are significantly higher than standard laboratory measurements, highlighting that the apparent quality of warfarin control is influenced by the measurement method.
INRatio-lab PT-INR discrepancy may prompt inappropriate warfarin adjustments; leaves open need for device validation in prospective cohorts.
Introduction: Various point-of-care (POC) devices are available for measurement of PT-INR with whole blood in patients receiving vitamin K antagonists (VKAs). However, the variability in values measured with various POC devices and traditional plasma-based laboratory measurement in clinical practice has yet to be clarified. Material and methods: PT-INR values measured with the same blood sample by POC devices of INRatio/INRatio 2 (INRatio) and the CoaguChek XS portable INR monitor (CoaguChek) were compared with those measured with traditional plasma-based laboratory measurement (lab-INR) in 1,347 measurements from 393 patients. The difference between the PT-INR values obtained from Lab-INR and POC devicees were expressed as Δ. To quantify the relationships among values obtained by various methods, regression analysis and the Bland-Altman method were applied. Results: PT-INR values measured with INRatio were higher than lab-INR with Δ = -0.33 ±0.38 (mean ± SD; 95% CI: -0.31 - -0.35). Pearson's correlation coefficient between the values measured with INRatio and lab-INR was 0.784. The PT-INR values measured with CoaguChek were not different from lab-INR with Δ -0.08 ±0.15 (mean ± SD; 95% CI: -0.07 - -0.09). The correlation between the value obtained with CoaguChek XS and lab PT-INR was high with Pearson's correlation coefficient 0.951. Conclusions: Even with the blood obtained from the same patients treated with the same dose of warfarin, the PT-INR values measured with INRatio were higher than traditional laboratory measurements. The apparent "quality of warfarin control" is influenced by the methods of PT-INR measurements.
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Komatsu et al. (2020) conducted a cross-sectional in Atrial fibrillation (patients receiving vitamin K antagonists) (n=393). Point-of-care PT-INR measurement (INRatio and CoaguChek XS) vs. Traditional plasma-based laboratory measurement (lab-INR) was evaluated on Difference (Δ) between lab-INR and INRatio PT-INR values (MD -0.33, 95% CI -0.31 - -0.35). PT-INR values measured with the INRatio point-of-care device were higher than traditional laboratory measurements, with a mean difference (Lab-INR minus INRatio) of -0.33.
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