A comparison of tools used for tuberculosis diagnosis in resource-limited settings: A case study at mubende referral hospital, Uganda

Abstract

Background: This study compared TB diagnostic tools and estimated levels of misdiagnosis in a resource-limited setting. Furthermore, we estimated the diagnostic utility of three-TB-associated predictors in an algorithm with and without Direct Ziehl-Neelsen (DZM). Materials and Methods: Data was obtained from a cross-sectional study in 2011 conducted at Mubende regional referral hospital in Uganda. An individual was included if they presented with a two weeks persistent cough and or lymphadenitis/ abscess. 344 samples were analyzed on DZM in Mubende and compared to duplicates analyzed on direct fluorescent microscopy (DFM), growth on solid and liquid media at Makerere University. Clinical variables from a questionnaire and DZM were used to predict TB status in multivariable logistic and Cox proportional hazard models, while optimization and visualization was done with receiver operating characteristics curve and algorithm-charts in Stata, R and Lucid-Charts respectively. Results: DZM had a sensitivity and specificity of 36.4% (95% CI = 24.9-49.1) and 97.1%(95% CI = 94.4-98.7) compared to DFM which had a sensitivity and specificity of 80.3%(95% CI = 68.7-89.1) and 97.1%(95% CI = 94.4-98.7) respectively. DZM false negative results were associated with patient's HIV status, tobacco smoking and extra-pulmonary tuberculosis. One of the false negative cases was infected with multi drug resistant TB (MDR). The three-predictor screening algorithm with and without DZM classified 50% and 33% of the true cases respectively, while the adjusted algorithm with DZM classified 78% of the true cases. Conclusion: The study supports the concern that using DZM alone risks missing majority of TB cases, in this case we found nearly 60%, of who one was an MDR case. Although adopting DFM would reduce this proportion to 19%, the use of a three-predictor screening algorithm together with DZM was almost as good as DFM alone. It's utility is whoever subject to HIV screening all TB suspects. © 2014 Muwonge et al.