Accuracy of a fluorescent dye-qPCR for diagnosis of pulmonary TB in HIV-associated adults

<sec><title>BACKGROUND</title>TB remains a major public health concern in Baja California, Mexico, where access to molecular diagnostics is limited.</sec><sec><title>METHODS</title>We evaluated the diagnostic performance of a fluorescent dye-based real-time quantitative PCR (SYBR-qPCR) assay targeting the IS6110 sequence for the detection of pulmonary TB (PTB). This was a cross-sectional diagnostic accuracy study conducted using sputum samples from 113 adults with clinical suspicion of PTB. Samples were analysed by acid-fast bacilli (AFB) smear microscopy, Löwenstein-Jensen culture as the reference standard, and SYBR-qPCR. Diagnostic performance was assessed using sensitivity, specificity, predictive values, and likelihood ratios. Receiver operating characteristic analysis was used to determine the optimal cycle threshold (Ct) cut-off.</sec><sec><title>RESULTS</title>SYBR-qPCR showed a sensitivity of 98.3% and a specificity of 92.5%. Sensitivity remained high among HIV-positive participants (96.6%), although specificity was lower (78.6%). In HIV-negative participants, both sensitivity and specificity exceeded 97%. The combination of SYBR-qPCR and AFB smear microscopy improved sensitivity (100%), and mean Ct values did not differ by HIV status.</sec><sec><title>CONCLUSION</title>SYBR-qPCR demonstrated consistent diagnostic performance across HIV strata, supporting its feasibility as a low-cost molecular tool for TB detection in resource-limited settings.</sec>.