Research

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

D N Prinsloo, T J Gould, C A Viljoen, W Basera, M Ntsekhe

Abstract


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.


Authors' affiliations

D N Prinsloo, Department of Medicine, Faculty of Health Sciences, University of Cape Town, South Africa

T J Gould, Head of Clinical Unit: Internal Medicine, George Regional Hospital, Department of Health, Western Cape, South Africa

C A Viljoen, Division of Cardiology, Department of Medicine, Faculty of Health Sciences, University of Cape Town, South Africa

W Basera, School of Public Health and Family Medicine, Faculty of Health Sciences, University of Cape Town, South Africa; and Burden of Disease Research Unit, South African Medical Research Council, Cape Town, South Africa

M Ntsekhe, Division of Cardiology, Department of Medicine, Faculty of Health Sciences, University of Cape Town, South Africa

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Keywords

Warfarin; INR control; Time in therapeutic range; Rural; Non-metropolitan; Primary healthcare

Cite this article

South African Medical Journal 2021;111(4):355-360. DOI:10.7196/SAMJ.2021.v111i4.15171

Article History

Date submitted: 2021-03-31
Date published: 2021-03-31

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