1130. Sputum volume production predicts clinical outcome in HIV-infected tuberculosis patients in Kampala, Uganda
Session: Oral Abstract Session: Lab Diagnostics
Friday, October 4, 2013: 3:00 PM
Room: The Moscone Center: 300
Background: Sputum acid-fast bacilli (AFB) smear microscopy results are commonly used as indicators of pulmonary tuberculosis (TB) severity as well as predictors for TB treatment response. The role of sputum smear in predicting TB treatment outcome is limited however by its poor sensitivity (particularly in HIV co-infected patients), indicating the need for more effective surrogate markers of TB outcome.  Sputum volume has not been previously studied as a potential determinant of treatment outcome.

Methods: This secondary analysis of prospectively collected data included sputum culture-positive pulmonary TB patients at an urban referral center in Kampala, Uganda who had at least one spot sputum volume measurement during the first two weeks of hospitalization. Demographics and clinical factors were assessed. An adjusted odds ratio (OR) was calculated for unsuccessful TB treatment outcome (defined as treatment failure, relapse, default or death) by a logistic regression analysis that was stratified by HIV serostatus.

Results: Of the 196 participants with spot sputum specimens who had sufficient microbiologic or demographic data to make a determination regarding their TB treatment outcome, 91 participants were HIV-infected and 105 were HIV uninfected.  In HIV-infected patients, unsuccessful TB treatment was associated with higher sputum volume at baseline (≥ 3 mL; OR 5.24, 95% CI 1.27-21.58, p = 0.02), cavitary disease on chest radiograph (OR 3.49, 95% CI 1.05-11.64, p = 0.04) and, post-secondary education (OR 6.84, 95% CI 1.72-27.23, p = 0.0006). Among the HIV-uninfected group, unsuccessful TB treatment was associated with resistance to any first or second-line antituberculous agent on baseline drug susceptibility testing (OR 6.22, 95% CI 2.12-18.24, p = 0.0001) but not with higher sputum volume (≥ 3 mL; OR 1.12, 95% CI 0.38-3.31, p = 0.83). 

Conclusion: Among HIV-infected individuals, there is significantly increased risk for unsuccessful TB treatment outcomes among those with higher baseline sputum spot volume (≥ 3 mL) in comparison to those  with lower sputum volume (<3 mL).  This association is not seen in HIV-uninfected individuals. Therefore, baseline sputum volume may be a unique predictor of unsuccessful TB outcome among HIV-positive patients in resource-poor regions.

Cassandra Pierre, MD1, Edward Jones-Lopez, MD1, Howard Cabral, PhD, MPH2 and C. Robert Horsburgh, MD3, (1)Infectious Diseases, Boston University School of Medicine, Boston, MA, (2)Biostatistics, Boston University School of Public Health, Boston, MA, (3)Epidemiology, Boston University School of Public Health, Boston, MA


C. Pierre, None

E. Jones-Lopez, None

H. Cabral, None

C. R. Horsburgh, None

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