Predictors of treatment failure among patients with smear positive pulmonary tuberculosis in the tuberculosis clinic in Mulago Hospital: a case control study

Abstract

Background: Treatment failure is a threat to the control of tuberculosis (TB) because of its association with Multi Drug Resistant tuberculosis (MDR TB) and also because affected patients continue to spread TB. Patients with treatment failure have a higher morbidity and mortality compared to those who are cured. The diagnosis of TB treatment failure is based on sputum smear microscopy at 5 months or later during treatment. Early identification of those at risk of treatment failure is important to prevent its occurrence. This can be done by frequent laboratory monitoring but this is not feasible in most resource limited settings. Clinicians may benefit from the knowledge of more easily measurable factors such as social, radiological, laboratory and treatment related factors that would predict treatment failure for early identification of those with a high risk of treatment failure. The limited resources for laboratory assessment would then be more effectively utilized among those with predictors of treatment failure. Primary objective: To identify the predictors of treatment failure among patients with smear positive PTB in Mulago hospital. Methodology: This was a case control study that was carried out in the TB (National TB and Leprosy Control Program-NTLP) clinic in Mulago hospital on sputum smear positive patients who had been on anti TB treatment for at least 5 months. The study was carried out between June and December 2007. Cases were selected consecutively until the sample size was attained. Two controls per case were selected consecutively until the sample size was attained. A pre-tested data-collecting tool was administered to the study subjects to determine the predictors of treatment failure. At analysis, cases and controls were compared for baseline characteristics. Predictors of treatment failure were determined by computing the odds ratio, the 95% confidence intervals and the p value. Results: Fifty cases and 100 controls were recruited into the study. Baseline characteristics were similar between the cases and the controls except that cases lived farther away from the TB clinic than the controls. Significant risk factors for treatment failure in this study included presence of cavities on baseline chest radiograph (OR 3.64, 95% CI 1.001-15.87), a positive sputum smear at 2 months of TB treatment (OR 20.26, 95%CI 3.67-111.86) and poor adherence to anti TB treatment (OR 13.2, 95%CI 2.24¬77.91). Conclusion: The predictors of treatment failure in patients attending the TB clinic in Mulago hospital are similar to those that have been identified in other settings in previous studies. Patients on anti TB treatment are likely to fail on treatment if they have cavities on baseline chest radiograph, if they have a positive sputum smear at 2 months of treatment or of they have poor adherence to treatment. Recommendations: Patients with the above risk factors for treatment failure should be prioritized for the use of limited laboratory resources for closer follow up during treatment to prevent treatment failure. The NTLP should find means of reminding clinicians and patients of the above risk factors and recommendations to improve treatment outcomes.