Optimal HAART adherence over time and time interval between successive visits: their association and determinants

Abstract

We aimed to investigate the determinants of optimal highly active antiretroviral therapy (HAART) adherence and time interval between successive clinic visits, and the association between these two processes. This was done by reviewing routinely collected patient information in the Centre for the AIDS Programme of Research in South Africa (CAPRISA). Records of 688 patients enrolled in the CAPRISA AIDS treatment (CAT) programme between 2004 and 2006 were analysed. Patients were considered adherent if they had taken at least 95% of their prescribed drugs. The adherence has been measured using the pill counts data. A multivariate generalised mixed random effects approach was used to jointly analyse optimal HAART adherence and time interval between successive visits. The results showed that on the overall, the association between optimal HAART adherence and time interval between successive visits was negative. The results further showed that the interaction between time and treatment site had a significant joint effect on optimal HAART adherence and time interval between successive visits. The interaction revealed that as the number of follow-up visits increased, the interval between successive visits also increased while at the same time high levels of optimal adherence were maintained in the rural treatment site. Moreover, after accounting for the time interval between successive visits, the results showed that optimal HAART adherence was significantly associated with having a cell phone, living with a partner as well as interactions that include time and gender, time and treatment site, age and gender and age and education. The findings provide evidence of a negative association between optimal HAART adherence and the time interval between successive clinic visits on the overall, which therefore indicates that longer time interval between successive clinic visits is undesirable if optimal HAART adherence is to be maintained. This notwithstanding, rural patients were able to maintain HAART adherence for longer time interval between successive clinic visits. Furthermore, the findings indicated that optimal HAART adherence was low for some sub-populations, such as the urban and male populations, thus vigorous ongoing adherence counseling is required.

Keywords:

• adherence rate
• adjusted odds ratio (aOR)
• joint modelling
• generalised mixed model
• pill counts method

Acknowledgements

CAPRISA was established in 2002 through a Comprehensive International Program of Research on AIDS (CIPRA) grant (AI51794) from the US National Institutes of Health (NIH), as a multi-institutional collaboration, incorporated as an independent non-profit AIDS Research Organisation. The NIH funded the development of the research infrastructure, including the data management, laboratory and pharmacy cores established through the CIPRA grant. The US PEPfAR grant (1U2GPS001350) funded the care of all the patients in the CAT Programme. Dikokole Maqutu was supported by the Columbia University-Southern African Fogarty AIDS International Training and Research Programme (AITRP) funded by the Fogarty International Center, NIH (grant no. D43TW00231). We gratefully acknowledge the patients in the CAT Programme. We also thank all the staff who worked on the CAT Programme, treating patients and helped in the data collection. Special thanks to the pharmacists for collection of pill count data.