International normalised ratio control in a non-metropolitan setting in Western Cape Province, South Africa

Prinsloo, Dawid Nicolaas

International normalised ratio control in a non-metropolitan setting in Western Cape Province, South Africa

Master Thesis

2021

Abstract

Background: The quality of INR control determines the effectiveness and safety of Warfarin. Data on INR control in non-metropolitan settings of South Africa (SA) is sparse. Objectives: To examine the Time in Therapeutic Range (TTR) and its potential predictors in a sample of Garden Route District Municipality INR clinics Methods: INR records from eight Primary Healthcare Clinics (PHCs) were reviewed. The TTR and percentage of patients with a TTR greater than 65% were determined. A host of variables were analysed for association with TTR. Results: The median age of the cohort of 191 was 56 years (IQR 44-69). The median TTR was 37.17% (IQR 20.21-58.78); only 17.8% of patients had a TTR > 65%. Compared to patients older than 50, those under 50 had worse INR control (TTR 26.63%, IQR 16.05-52.98 vs. 43.5%, IQR 23.52- 60.08, p=0.01). Patients hospitalised for any reason during the study period had worse INR control than patients not hospitalised (TTR 26.23%, IQR 16.24-50.16 vs. 42.89, IQR 23.5-61.95, p=0.02). On multivariable regression analysis, participants on warfarin for atrial fibrillation/flutter had better INR control (OR 2.21, CI 1.02-4.77, p=0.04) but the control was still very poor. Conclusion: INR control as determined by TTR and proportion of TTR >65% in these non-metropolitan clinics was poor. Age and markers of illness predicted poor control. There was a difference in control between groups depending on the indication for warfarin. Evidence-based measures to improve the quality of INR control amongst patients on warfarin therapy need to be instituted as a matter of urgency.

Keywords

Medicine

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