ASSOCIATION OF INR QUALITY WITH COMPLICATIONS AMONG PATIENTS ON WARFARIN THERAPY IN HOSPITAL SULTAN ISMAIL PETRA, KELANTAN STATE

Abstract

Background: Poor International Normalised Ratio (INR) quality of warfarin (time in therapeutic range (TTR) <70%) can lead to increased risk of complications (bleeding/thromboembolism). However, the association of INR quality (TTR) with warfarin complications in Hospital Sultan Ismail Petra (HSIP) is not well established. This study aimed to investigate the INR quality using TTR and its association with complications among patients on warfarin therapy in HSIP.

Materials and Methods: A total of 117 patients were recruited from INR Clinic and were retrospectively traced from the medical records office. TTR was computed using Rosendaal method and categorized into two groups (<70% or ≥ 70%). Clinical complications assessed were bleeding or thromboembolism (TE), defined based on hospitalization.  Patients were followed from warfarin initiation to the first occurrence of complication. Chi-square test was used to evaluate the association of TTR with complications.

Result: Mean TTR was 55% with 57.3% of the total patients had TTR <70%. During observation, 12 complications (5 bleedings, 7 thromboembolisms) occurred in 10% of the patients, and those with TTR <70% were at higher risk. Patients with TTR <70% had a higher risk for any bleeding (RR: 2.99; 95% CI: 0.34 – 25.90) but a lower risk for any thromboembolism (RR: 0.56; 95% CI: 0.13 – 2.39). However, no statistically significant association was observed between TTR and overall complications (p = 0.94).

Conclusion: Bleeding and thromboembolism complications were associated with warfarin therapy, independently of INR control (TTR). Future study with a larger sample size is warranted to further validate this study’s finding.

Keywords: warfarin, TTR, bleeding, thromboembolism, complications