Clinical Pharmacology and Therapeutics
Clinical Pharmacology and Therapeutics
5 years ago

The international normalized ratio (INR): What reagent, what instrument? The assessment of the agreement between INR values according to different reagent/instrument combinations

The international normalized ratio (INR): What reagent, what instrument? The assessment of the agreement between INR values according to different reagent/instrument combinations
H. Baccouche, N. Ben Romdhane, S. Mahjoub, A. Zoghlami, A. Chakroun
What is known and objective The international normalized ratio (INR) is widely used to monitor patients on vitamin K antagonists. This study aimed to assess the agreement of INR values obtained with different thromboplastin/instrument combinations. Material and methods International normalized ratio was determined on plasmas from 330 patients undergoing antivitamin K treatment (with acenocoumarol), using two calibration methods and four reagent/instrument combinations: Both Neoplastine CI and Neoplastine CI Plus on STA-R instrument from Diagnostica STAGO, Asnières, France; and both Thromborel S and Innovin on SYSMEX 2100i instrument from Siemens Health Care Diagnostics, Marbung, Germany. The agreement analysis was done using the Bland-Altman plot and the Cohen Kappa coefficient. Results The mean of the differences between the INR values and the limits of agreement were −0.07 [−0.51 to 0.38] for the Neoplastine CI plus and Neoplastine CI reagents, −0.08 [−1.18 to 1.03] for the Thromborel S and Innovin reagents when the INR was calculated, −0.1 [−1.15 to 0.95] for the Thromborel S and Innovin reagents when the INR was directly calibrated and −0.1 [−0.7 to 0.5] for the Neoplastine CI plus and Thromborel S. Cohen's kappa coefficients were 0.94, 0.76, 0.85 and 0.82, respectively. New findings and conclusion The agreement between the four reagent/instrument combinations was high enough to classify patients as inefficaciously or efficaciously anticoagulated. The data interpretation should always be related to the clinical purpose. According to this study, it appears that obtaining the same INR value with different combinations (reagent/instrument) is not possible. However, the agreements between four reagent/instrument combinations were high enough to allow their interchangeable use for classifying patients as satisfactorily or unsatisfactorily anticoagulated.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/jcpt.12608

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