A range of factors influence patients' adherence to the lengthy and complex treatment regimens used for tuberculosis (TB), according to a systematic review of the evidence, and better knowledge of these may allow the development of interventions to reduce barriers to adherence. The authors of the review note that TB remains a major contributor to the global burden of disease, and requires treatment with multiple drugs for prolonged courses. As a result, up to half of patients do not complete the course of treatment leading to prolonged infection, the development of resistant organisms, and adverse outcomes for both individual and their society. This review aimed to identify research on factors that both hinder and encourage patients to adhere to their treatment, with the objective of informing the development of new interventions to improve adherence.
The authors carried out a comprehensive literature search for studies that examined adherence or non-adherence to preventive or curative TB treatments and described the perspectives of patients, care givers, or health care providers. Both qualitative and quantitative studies were included, and unpublished work was considered. The only major limitation was the exclusion of papers not published in English due to resource constraints.
Over 7,000 citations were scanned and 2,162 potentially relevant abstracts obtained. Of these, 626 were considered potentially eligible after review of the abstracts and scanned in full to produce 66 potentially eligible studies: exclusion of duplicate and ineligible papers, left 44 for final review and assessment. They ranged in publication date from 1969 to 2005, covered most geographical areas, and involved about 3,213 individuals. Eligible studies were used to develop a model of factors related to treatment adherence: studies were analysed to identify relevant themes and concepts, and categories were developed from these to represent related themes and concepts. Eight major themes were identified across the studies, including organisation of treatment and care; interpretations of illness and wellness; the financial burden of treatment; knowledge, attitudes, and beliefs about treatment; law and immigration; personal characteristics and adherence behaviour; side effects; and family, community, and household support. The authors used these to produce a synthesis describing how four major factors interact to affect adherence to TB treatment: structural factors, including poverty and gender discrimination; the social context; health service factors; and personal factors. They discuss these in some depth, noting areas of interaction between different factors. Finally, they suggest some implications of the study for policy and practice. They note that the results are limited by the underlying data. Additionally, most studies were carried out in developing countries and are thus most relevant to these; nevertheless, studies in more developed countries had similar findings so the overall results may be applicable to them also.
Overall, the authors conclude that adherence to TB medication is complex and dynamic, with a wide range of factors impacting on patients' treatment-taking behaviour. They suggest that their analysis could help in the development of both patient-centred and structural interventions to assist adherence.
PLoS Med 2007; 4(7): e238. doi:10.1371/journal.pmed.0040238 (link to free full text)