RESUMO
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.
