Abstract
BackgroundThe Xpert MTB/RIF (Xpert) assay technology allows rapid and sensitive diagnosis of pulmonary tuberculosis (PTB) from sputum specimens. However, diagnosis of PTB is difficult for patients who cannot produce sputum. The objective of this study was to investigate the use of Xpert assay for successful detection of PTB using stool samples from adult subjects.MethodsBoth stool and sputum samples from known smear and Xpert positive PTB patients were collected from a TB hospital in Dhaka. Stool samples were collected from healthy individuals without TB symptoms from a slum area of Dhaka. Stool and sputum samples were decontaminated and concentrated using NALC-NaOH-Na-citrate solution and the resultant sediment was used for Xpert, acid-fast bacilli (AFB) microscopy and culture.ResultsA total of 102 stool samples were collected from PTB patients and another 50 stool samples from healthy individuals without TB. The sensitivity of the Xpert assay for detection of M. tuberculosis in stool samples of PTB patients was 90.2% (95% CI, 82.9–95.0). All 50 stool samples from healthy individuals were negative by the assay (Specificity 100%; 95% CI, 92.9–100). Compared with the sputum culture positive results the sensitivity of the stool Xpert assay was 94.8% (95% CI, 88.5–97.8). Moreover, stool Xpert demonstrated full concordant results with the sputum culture for detection of rifampicin susceptibility. The cycle threshold values of rpoB probes obtained from Xpert assay correlated significantly with the bacilli load in the corresponding stool (Spearman correlation = -0.40, P < 0.01) and sputum (Spearman correlation = -0.77, P < 0.01) samples as determined by microscopy.ConclusionsStool Xpert can be applied as a potential alternative of sputum testing for detection of M. tuberculosis and accurate determination of RIF susceptibility in adult PTB patients. The assay would be beneficial for rapid diagnosis of PTB for those adult patients who cannot expectorate sputum.
Highlights
Tuberculosis (TB) is a lethal infectious disease caused by Mycobacterium tuberculosis, which is the leading cause of death from a single infectious agent worldwide [1]
The sensitivity of the Xpert assay for detection of M. tuberculosis in stool samples of pulmonary TB (PTB) patients was 90.2%
All 50 stool samples from healthy individuals were negative by the assay (Specificity 100%; 95% CI, 92.9–100)
Summary
Tuberculosis (TB) is a lethal infectious disease caused by Mycobacterium tuberculosis, which is the leading cause of death from a single infectious agent worldwide [1]. Early detection and determining the anti-TB drug susceptibility is essential for successful treatment and control of the disease. In resource poor settings with high TB burden, there is an urgent need for implementing a new rapid diagnostic method for detecting TB. The Xpert technology allows rapid and relatively sensitive diagnosis of pulmonary TB (PTB) in sputum specimens [8, 9]. Diagnosis of PTB is difficult for patients who cannot produce sputum, a problem that is common in young children, HIV-positive and elderly patients [10]. The Xpert MTB/RIF (Xpert) assay technology allows rapid and sensitive diagnosis of pulmonary tuberculosis (PTB) from sputum specimens. Diagnosis of PTB is difficult for patients who cannot produce sputum.
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