SMaRT-PCR: sampling using masks and RT-PCR, a non-invasive diagnostic tool for paediatric pulmonary TB

<sec id="st1"><title>BACKGROUND</title>Key challenges in paediatric TB diagnosis are invasive sampling and poor sensitivity of standard methods. This study demonstrates the diagnostic potential of non-invasive sampling of bioaerosols from children using SMaRT-PCR, comprising mask sampling combined with reverse transcriptase-polymerase chain reaction (RT-PCR) for TB.</sec><sec id="st2"><title>METHODS</title>Exhaled bioaerosols were captured on modified N-95 masks in a 10-min talk-cough-breathe process from 51 children (30 with TB confirmed using standard sampling methods and 21 without TB) aged 2–15 years. All mask samples were tested using in-house RT-PCR for 16s and rpo B RNA transcripts. Additional mask samples from children with TB were tested using Xpert ® MTB/RIF ( n = 3) and Xpert ® MTB/RIF Ultra ( n = 27).</sec><sec id="st3"><title>RESULTS</title>SMaRT-PCR sensitivity for detecting TB among treatment-naïve children was 96% if 16s or rpo B was present, and 75% if both genes were present, comparable to standard methods (71%) in the same cohort. Specificity was better for both genes, at 95%, than 85% for a single gene detection. Mask sampling with Xpert MTB/RIF or Ultra had a sensitivity of only 13%.</sec><sec id="st4"><title>CONCLUSION</title>This is the first study to provide evidence for testing bioaerosols as a promising alternative for detecting paediatric TB. Sampling is non-invasive and simple, with the potential for point-of-care applications. This pilot study also suggests that RNA transcript-based detection may improve TB diagnostic sensitivity in children; however, further investigation is required to establish its adaptability in clinical settings.</sec>