TITLE:
Analytical Agreement and Treatment-Decision Concordance between Capillary Point-of-Care and Laboratory INR Testing in Patients Receiving Vitamin K Antagonists: A Prospective Method-Comparison Study
AUTHORS:
Bénédicte Carine Boka, Patrick Coffie, Joël Lévi One, Fatoumata Traore, Yvec N'Da Kouakou N’goran, Marie-Catherine Yapi, Yah Nina Estelle Andjou, Roland N’guetta, Duni Sawadogo
KEYWORDS:
International Normalized Ratio, Vitamin K Antagonists, Point-of-Care Testing, Capillary Blood, Method Comparison, Anticoagulation
JOURNAL NAME:
World Journal of Cardiovascular Diseases,
Vol.16 No.10,
October
21,
2026
ABSTRACT: Background: Vitamin K antagonists remain widely used in sub-Saharan Africa, particularly among patients with mechanical prosthetic valves and rheumatic valvular disease. In many services, INR monitoring still depends on a central laboratory, which can delay treatment decisions. We compared capillary point-of-care and venous laboratory INR measurements and examined whether the two methods led to the same treatment-decision category. Methods: This prospective study followed 101 patients receiving vitamin K antagonists over 131 consecutive INR monitoring visits at a tertiary cardiovascular referral centre in West Africa. At each visit, capillary and venous INR measurements were obtained within two minutes of each other. Agreement between the two methods was assessed with repeated-measures Bland-Altman analysis. We also examined whether the two results would lead to the same treatment decision: keeping the dose unchanged, increasing it, or reducing it. Results: Two venous results remained right-censored as >6, leaving 129 exact pairs for the primary continuous analysis. The mean capillary-minus-venous bias was +0.09 INR units, with repeated-measures 95% limits of agreement from −0.89 to +1.06. Variability increased at higher INR values. Treatment decisions agreed in 108 of 131 episodes (82.4%); Cohen’s kappa was 0.731 (patient-cluster bootstrap 95% CI 0.627 - 0.826). All 23 discordances were minor, and no episode produced opposite dose directions. Conclusion: Overall, capillary point-of-care INR testing gave results that were close to laboratory measurements and led to the same treatment decision in most monitoring episodes. Differences were more noticeable when INR values were high, but none of the discordant results suggested opposite dose adjustments. Taken together, these findings support supervised point-of-care testing as a practical option for routine INR monitoring, especially in areas where access to laboratory services is limited. Reliable quality control remains important, with laboratory confirmation mainly needed for high, unexpected, or borderline results.