article · Journal of International Medical Research
A study across five tuberculosis clinics in Dar es Salaam evaluated the diagnostic accuracy of Ziehl-Neelsen sputum smear microscopy compared with Löwenstein-Jensen culture. The investigation focused on 200 adults who had already tested positive for tuberculosis via the Xpert Mycobacterium tuberculosis and rifampicin assay. When measured against culture as the reference standard, smear microscopy demonstrated a sensitivity of 86.6 percent and a specificity of 40.7 percent, yielding an area under the receiver operating characteristic curve of 0.64. Notably, 43 percent of patients with negative smear microscopy results were actually positive on culture. These results reveal significant diagnostic gaps when relying solely on smear microscopy. The findings highlight the operational value of the Xpert assay and suggest that selectively combining Xpert with culture can improve case detection in resource-constrained environments where newer diagnostic tools remain out of reach.
Accurate tuberculosis testing is critical for timely treatment and stopping community transmission. This research demonstrates that traditional smear microscopy fails to detect a large proportion of active tuberculosis cases confirmed by culture. Relying on molecular tests like Xpert, alongside selective culturing, helps clinics avoid missed diagnoses and ensures infected individuals receive prompt and appropriate medical care in low-resource environments.
The findings inform diagnostic workflows and procurement decisions for public health organisations, clinical laboratories, and healthcare providers in low-resource settings. This represents applied clinical research with immediate operational relevance, guiding how existing, commercially available diagnostic tools such as Xpert assays and culture systems should be deployed together to optimise case detection where advanced platforms remain inaccessible.
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Objective To assess the diagnostic accuracy of sputum smear microscopy compared with culture in patients who were already confirmed positive for tuberculosis by Xpert Mycobacterium tuberculosis /rifampicin assay in Tanzania. Methods A cross-sectional study was conducted across five tuberculosis clinics in Dar es Salaam. Adults (aged 18–80 years) with symptoms of tuberculosis and a positive Xpert Mycobacterium tuberculosis /rifampicin assay result provided additional sputum specimens for smear microscopy using Ziehl–Neelsen staining and culture on Löwenstein–Jensen medium, processed at the Central Tuberculosis Reference Laboratory, Muhimbili National Hospital. Results We enrolled 200 participants, with a median age of 35 (interquartile range: 27–46) years; 74.5% of them were male. Using culture as the reference, Ziehl–Neelsen smear microscopy showed a sensitivity of 86.6% and a specificity of 40.7%. The Xpert Mycobacterium tuberculosis /rifampicin assay showed higher diagnostic accuracy. Notably, 43% of smear-negative cases were culture-positive, indicating that smear microscopy alone led to a substantial proportion of missed diagnoses. The Ziehl–Neelsen smear’s receiver operating characteristic curve had an area under the curve of 0.64, indicating moderate performance. Conclusion This study underscores the limitations of smear microscopy and highlights the operational utility of Xpert Mycobacterium tuberculosis /rifampicin assay. In regions where Xpert Ultra remains inaccessible, combining Xpert with culture selectively may enhance detection in low-resource settings.
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DOI: 10.1177/03000605251390703
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