Review
Clinical diagnosis of smear-negative pulmonary tuberculosis in low-income countries: the current evidence

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Summary

Sputum smear examination for acid-fast bacilli (AFB) can diagnose up to 50–60% of cases of pulmonary tuberculosis in well-equipped laboratories. In low-income countries, poor access to high-quality microscopy services contributes to even lower rates of AFB detection. Furthermore, in countries with high prevalence of both pulmonary tuberculosis and HIV infection, the detection rate is even lower owing to the paucibacillary nature of pulmonary tuberculosis in patients with HIV infection. In the absence of positive sputum smears for AFB, at primary care level, most cases of pulmonary tuberculosis are diagnosed on the basis of clinical and radiological indicators. This review aims to evaluate various criteria, algorithms, scoring systems, and clinical indicators used in low-income countries in the diagnosis of pulmonary tuberculosis in people with suspected tuberculosis but repeated negative sputum smears. Several algorithms and clinical scoring systems based on local epidemiology have been developed to predict smear-negative tuberculosis. Few of these have been validated within the local context. However, in areas where smear-negative tuberculosis poses a major public-health problem, these algorithms may be useful to national tuberculosis programmes by providing a starting point for development their own context-specific diagnostic guidelines.

Section snippets

Methods

We identified relevant publications by searches of Medline, PubMed, Embase, HealthSTAR, and Web of Science with the keywords: “tuberculosis”, “Mycobacterium tuberculosis”, “sputum negative”, “smear negative”, AFB negative”, “negative for AFB”, “abacillary”, and “diagnosis” for papers published in English from 1966 onwards. We also searched for relevant articles in the contents tables of the International Journal of Tuberculosis and Lung Diseases for the past 10 years. We examined the reference

Results

We selected 15 studies that met the above criteria. Table 1 gives an outline of the studies and table 2 summarises the validity and clinical usefulness of each. Most studies validated diagnostic tools or criteria against sputum culture. However, several studies included in this review also used other less recognised methods of confirming the diagnosis of pulmonary tuberculosis.

Search strategy and selection criteria

These are described in detail in the Methods section.

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