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CARDIOLOGY / CLINICAL RESEARCH
Variability of PT-INR values measured by point of care devices INRatio/INRatio 2 and CoaguChek XS and standard laboratory method. A cross-sectional study
1
Komatsu Cardiovascular Clinic, Hadano, Japan
2
Department of Medicine (Cardiology), School of Medicine, Tokai University, Isehara,
Japan
Submission date: 2020-07-09
Final revision date: 2020-08-06
Acceptance date: 2020-08-17
Online publication date: 2020-09-21
Publication date: 2026-04-30
Corresponding author
Shinya Goto
Department of Medicine (Cardiology) School of Medicine Tokai University 143 Shimokasuya Isehara 259-1193 Japan Phone: +81 463-93-1121 Fax: +81 463+93-6679
Department of Medicine (Cardiology) School of Medicine Tokai University 143 Shimokasuya Isehara 259-1193 Japan Phone: +81 463-93-1121 Fax: +81 463+93-6679
Arch Med Sci 2026;22(2):743-749
KEYWORDS
TOPICS
ABSTRACT
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 D. 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 D = –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 D –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.
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 D. 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 D = –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 D –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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