Abstract
Timely diagnosis of paucibacillary tuberculosis (TB) which includes smear-negative pulmonary TB (PTB) and extra-pulmonary TB (EPTB) remains a challenge. This study was performed to assess the diagnostic utility of stool as a specimen of choice for detection of mycobacterial DNA in paucibacillary TB patients in a TB-endemic setting. Stool samples were collected from 246 subjects including 129 TB patients (62 PTB and 67 EPTB) recruited at TB hospital in Delhi, India. Diagnostic efficacy of stool IS6110 PCR (n = 228) was measured, using microbiologically/clinically confirmed TB as the reference standard. The clinical sensitivity of stool PCR was 97.22% (95% confidence interval (CI), 85.47-99.93) for detection of Mycobacterium tuberculosis in stool samples of smear-positive PTB patients and 76.92% (CI, 56.35–91.03) in samples from smear-negative PTB patients. Overall sensitivity of PCR for EPTB was 68.66% (CI, 56.16–79.44), with the highest sensitivity for stool samples from patients with lymph node TB (73.5%), followed by abdominal TB (66.7%) and pleural effusion (56.3%). Stool PCR presented a specificity of 95.12%. The receiver operating characteristic curve also indicated the diagnostic utility of stool PCR in TB detection (AUC: 0.882). The performance characteristic of the molecular assay suggests that stool DNA testing has clinical value in detection of TB.
Highlights
Diagnosis of paucibacillary tuberculosis (TB) which includes smear-negative pulmonary TB (PTB) and extra-pulmonary TB (EPTB) remains a challenge
The present study aims to evaluate the effectiveness of stool sample for Mycobacterium tuberculosis (Mtb) detection in varied TB cases by polymerase chain reaction (PCR) amplification of insertion element IS6110 in 228 subjects
We recruited two different categories of patients: 1) PTB and EPTB treatment-complete patients (TC) who had completed the standard anti-tubercular treatment (ATT) regimen (n = 39), and 2) non-TB respiratory patients diagnosed with asthma and chronic obstructive pulmonary disease (n = 19)
Summary
Diagnosis of paucibacillary tuberculosis (TB) which includes smear-negative pulmonary TB (PTB) and extra-pulmonary TB (EPTB) remains a challenge. This study was performed to assess the diagnostic utility of stool as a specimen of choice for detection of mycobacterial DNA in paucibacillary TB patients in a TB-endemic setting. Apart from the diagnostic and treatment difficulties faced in the eradication of PTB, timely diagnosis and treatment of EPTB is considered a bigger challenge. This is due to the diverse, non-specific and paucibacillary presentation of EPTB at remote body sites and requirement of a longer treatment regimen[2]. Molecular tests with alternate clinical samples, that are easy to obtain, safer, and give uniform results, are warranted Assays such as tuberculin skin test and T-cell based interferon-gamma release assay find limited utility in TB diagnosis in endemic countries like India. In a pilot run of 36 samples, stool Xpert testing was done for patients with PTB and EPTB to check for adaptability of stool testing in a tertiary healthcare setting
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