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Assessment of anticoagulation management in outpatients attending a warfarin clinic in Windhoek, Namibia

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Abstract

Background

Warfarin, an anticoagulant with a low therapeutic index, requires frequent international normalized ratio (INR) monitoring to ensure efficacy and safety. Little is known about anticoagulation management in Namibia.

Objective

The purpose of this study was to investigate the level of anticoagulation control among outpatients requiring maintenance warfarin therapy.

Setting

Clinical records of patients attending the warfarin anticoagulation clinic at Windhoek Central Hospital (Windhoek, Namibia) during a 1-year period were reviewed.

Methods

Of the 294 outpatients who visited the warfarin anticoagulation monitoring clinic in 2017, 215 patients were included in the data analysis. The following information was available and used for data analysis: age and sex of the patient, indication for warfarin use, number of visits, warfarin dose and INR values. The individual’s time in therapeutic range (iTTR) was the primary outcome, which was calculated both using the Rosendaal method and as the percentage of the reported INR values in the therapeutic range.

Results

The patients’ mean iTTR was 29.4%, well below the 65% target, when estimated by the Rosendaal method and 25.2% when calculated as the percentage of INR values within the therapeutic range. Only 22 of the 215 patients (10%) had an iTTR ≥ 65%.

Conclusions

Anticoagulation control at this outpatient clinic was low relative to the target iTTR of 65%. Consequently, patients were at risk for further embolic events or bleeding events based on the high numbers of sub- and supratherapeutic INRs during the time period studied.

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Acknowledgements

The authors would like to acknowledge the invaluable help of the nursing staff at the Warfarin Clinic (Cardiac Clinic) of Windhoek Central Hospital.

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Authors and Affiliations

  1. School of Pharmacy, University of Namibia, Windhoek, Namibia

    Lauren J. Jonkman, Marvelous P. Gwanyanya, Roger K. Verbeeck & Bonifasius S. Singu

  2. School of Pharmacy, University of Pittsburgh, Pittsburgh, USA

    Lauren J. Jonkman

  3. Warfarin Clinic, Windhoek Central Hospital, Windhoek, Namibia

    Monika N. Kakololo

Authors
  1. Lauren J. Jonkman
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  2. Marvelous P. Gwanyanya
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  3. Monika N. Kakololo
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  4. Roger K. Verbeeck
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  5. Bonifasius S. Singu
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Corresponding author

Correspondence to Bonifasius S. Singu.

Ethics declarations

Ethics approval

The study was approved by the human ethics committees of the University of Namibia and of the Ministry of Health & Social Services, Namibia.

Conflict of interest

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

This study received no specific funding. L.J. Jonkman was supported by a Fulbright Scholarship.

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Jonkman, L.J., Gwanyanya, M.P., Kakololo, M.N. et al. Assessment of anticoagulation management in outpatients attending a warfarin clinic in Windhoek, Namibia. Drugs Ther Perspect 35, 341–346 (2019). https://doi.org/10.1007/s40267-019-00630-y

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  • DOI: https://doi.org/10.1007/s40267-019-00630-y

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