Unannounced phone-based pill counts for monitoring antiretroviral medication adherence in South Africa

Abstract

Background

Unannounced phone-based pill counts (UPC) are an objective measure of medication adherence that may be used in resource limited settings. The current study reports the feasibility and validity of UPC for monitoring antiretroviral therapy (ART) adherence among people living with HIV in South Africa. People living with HIV (N = 434) in an economically impoverished township and receiving ART for at least 3-months completed: two UPC in a one-month period; measures of clinic and medication experiences; and provided blood samples for HIV viral load and CD4 testing. Analyses compared two methods for managing values of over-dosing (> 100%), specifically censoring values to 100% (> 100% = 100%) vs. subtracting over-dosing from two months of perfect adherence (200% - > 100% value).

Results

Findings showed that two UPC calls were successfully completed with 91% of participants in a one-month period. The average number of call attempts needed to reach participants was 2.4. Results showed that lower UPC adherence was significantly associated with male gender, alcohol use, higher HIV viral loads, lower CD4 cell counts, running out of ART, and intentionally not taking ART. Comparisons of methods for adjusting over-dosing found subtraction yielding a better representation of the data than censoring.

Conclusions

UPC were demonstrated feasible and valid with patients receiving ART in a resource limited setting and offers a viable method for objectively measuring ART adherence in these settings.

Keywords:

• Adherence
• adherence measurement
• HIV treatment
• medication monitoring
• objective measurement
• clinical trials

Acknowledgments

The authors appreciate the involvement of the City of Cape Town clinics that participated in this research.

Authors’ contributions

SK and CM conceptualized the study design, conducted data analyses and contributed to the writing of the paper. EB, BS and MK oversaw scientific execution of the study, contributed to the conceptualization of the study design, and contributed to the writing of the paper. All authors read and approved the final manuscript.

Disclosure statement

The authors declare no competing interests.

Data availability statement

Data are retained by the authors and available upon reasonable request.

Additional information

Funding

This work was supported by the National Institute of Mental Health (NIMH) Grant R01MH19913.