Effect of chronic kidney disease on warfarin responsiveness among Thai patients

This study aims to determine the effect of chronic kidney disease on warfarin response, including initial doses, maintenance doses, time in therapeutic range (TTR), and international normalized ratio (INR) variability. This is a retrospective cohort study at Rajavithi Hospital from 2015 to 2018. A total of 189 patients were included and divided into five groups based on estimated glomerular filtration rate (eGFR) (G1, eGFR ≥ 60 mL/min/1.73 m2; G2, 30–59 mL/min/1.73 m2; G3, 15–29 mL/min/1.73 m2; G4, ≤ 15 mL/min/1.73 m2; and G5, ≤ 15 mL/min/1.73 m2 with dialysis). The median age was 65.00 years, and 60.9% of patients were female. The median (interquartile range) of initial warfarin doses were 17.50 (14.0, 21.0) mg/week, and average doses for achieved target INR were 19.00 (14.0, 25.0) mg/week in all groups. The initial warfarin doses were not different among groups but the maintenance doses were significantly different (P = 0.001). The median of INR variability was 0.16, which was not significantly different and TTR was 69.00%. Patients with CKD used lower average targeted doses of warfarin and had lower TTR than those with normal renal function. Interestingly, this study revealed that eGFR ≥60 ml/min/1.73 m2 and female sex affected TTR by more than 60%.