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

Background. The quality of international normalised ratio (INR) control determines the effectiveness and safety of warfarin therapy. Data on INR control in non-metropolitan settings of South Africa (SA) are sparse. Objectives. To examine the time in therapeutic range (TTR) and its potential predictors in a sample of Garden Route District Municipality primary healthcare clinics (PHCs). Methods. INR records from eight PHCs were reviewed. The TTR and percentage of patients with a TTR >65% were determined. A host of variables were analysed for association with TTR. Results. The median (interquartile range (IQR)) age of the cohort ( N =191) was 56 (44 - 69) years. The median (IQR) TTR was 37.2% (20.2 - 58.8); only 17.8% of patients had a TTR ≥65%. Compared with patients aged >50 years, those aged <50 had worse INR control (median (IQR) TTR 26.6% (16.1 - 53.0) v. 43.5% (23.5 - 60.1); p =0.01). Patients hospitalised for any reason during the study period had worse INR control than patients not hospitalised (median (IQR) TTR 26.2% (16.2 - 50.2) v. 42.9% (23.5 - 62.0); p =0.02). On multivariable regression analysis, participants on warfarin for atrial fibrillation/flutter had better INR control than those with other indications for warfarin (odds ratio 2.21; 95% confidence interval 1.02 - 4.77; p =0.04), but the control was still very poor. Conclusions. INR control, as determined by TTR and proportion of TTR ≥65%, in these non-metropolitan clinics was poor. Age and hospitalisation as a marker 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 in patients on warfarin therapy need to be instituted as a matter of urgency.