INR Variability and Time in Therapeutic Range in Warfarin – Treated Patients with Chronic Kidney Disease: A Retrospective Cohort Study Using Electronic Database

Abstract

Background: Warfarin has been used for treatment and prevention of systemic thromboembolism in various indications. Several factors can affect to warfarin response, but the association between chronic kidney disease (CKD) and warfarin response has been limited. Objectives: To determine the relationship between INR variability and CKD and time in therapeutic range (TTR) and CKD. Methods: This was a retrospective cohort study at Rajavithi Hospital during January 2017 to June 2020. The inclusion criteria were 1) outpatients older than 18 years of age 2) taking warfarin for the first time at Rajavithi Hospital and 3) to follow up the treatment continuously in Rajavithi Hospital until the INR values were achieved the target range at least 2 consecutive times. The patients were divided by eGFR into 2 groups (group 1: eGFR ≥ 60 ml/min/1.73 m² and group 2: eGFR < 60 ml/min/1.73 m² without renal replacement therapy). The data were analyzed by using SPSS program version 22.0. Results: A total of 390 patients were identified. The mean age was 61.0017.39 years old and 55.64% were females. Each patient was classified by eGFR into 2 groups (group 1; n = 260 (66.67%) and group 2; n = 130 (33.33%), respectively). The median of INR variability was 0.15 with significant difference and the median of TTR was 60.22% with not significant difference between two groups. Conclusions: Our study showed that INR variability was significantly different in each group while TTR was not significantly different among studied groups. CKD patients had lower INR variability and TTR than the normal kidney function group.