Open Access Research article

Adherence with isoniazid for prevention of tuberculosis among HIV-infected adults in South Africa

Tom A Szakacs1*, Douglas Wilson2, D William Cameron2, Michael Clark1, Paul Kocheleff2, F James Muller2 and Anne E McCarthy1

Author Affiliations

1 Division of Infectious Diseases, University of Ottawa at The Ottawa Hospital, 501 Smyth Rd., K1H 8L6, Ottawa, Canada

2 Department of Medicine, Pietermaritzburg Hospital Complex, Greys Hospital, 3200 Townbush Rd., Pietermaritzburg, South Africa

For all author emails, please log on.

BMC Infectious Diseases 2006, 6:97  doi:10.1186/1471-2334-6-97

Published: 13 June 2006



Tuberculosis (TB) is the most common opportunistic infection in HIV-infected adults in developing countries. Isoniazid (INH) is recommended for treatment of latent TB infection, however non-adherence is common. The purpose of this study was to apply in-house prepared isoniazid (INH) urine test strips in a clinical setting, and identify predictors of positive test results in an adherence questionnaire in HIV-infected adults taking INH for prevention of TB.


Cross-sectional study of adherence using a questionnaire and urine test strips for detection of INH metabolites at two hospitals in Pietermaritzburg, South Africa. Participants were aged at least 18 years, HIV positive, and receiving INH for prevention of tuberculosis disease. Univariate and multivariate analyses are used to identify factors relevant to adherence.


301 consecutive patients were recruited. 28% of participants had negative urine tests. 32 (37.2%, 95% CI25.4, 45.0) of the 86 patients who received INH from peripheral pharmacies said the pharmacy had run out of INH at some time, compared with central hospital pharmacies (p = 0.0001). In univariate analysis, a negative test was associated with self-reported missed INH doses (p = 0.043). Each 12-hour increment since last reported dose increased the likelihood of a negative test by 34% (p = 0.0007). Belief in INH safety was associated with a positive test (p = 0.021). In multivariate analysis, patients who believed INH is important for prevention of TB disease were more likely to be negative (p = 0.0086).


Adequate drug availability at peripheral pharmacies remains an important intervention for TB prevention. Key questions may identify potentially non-adherent patients. In-house prepared urine tests strips are an effective and cheap method of objectively assessing INH adherence, and could be used an important tool in TB control programs.