Combination of exhaled breath condensate samples with lipoarabinomannan point of care assay for pulmonary tuberculosis (TB) diagnosis: protocol for a diagnostic accuracy study

Abstract

Introduction The WHO estimates a gap of about 30% between the incident (10.6 million) and notified (7.5 million) cases of tuberculosis (TB). Combined with the growing recognition in prevalence surveys of the high proportion of cases identified who are asymptomatic or paucisymptomatic, these data underscore how current symptom screening approaches and use of diagnostic tests with suboptimal performance on sputum miss large numbers of cases. Thus, the development of sputum-free biomarker-based tests for diagnosis is becoming necessary, which the WHO has already identified as a priority for new TB diagnostics.The objective of this study is to evaluate a combination of exhaled breath condensate (EBC) samples and mycobacterial lipoarabinomannan (LAM) as point-of-care (POC) assays to identify TB patients.Methods and analysis This prospective diagnostic accuracy study is conducted at the TB Screening and Treatment Centre of International Center for Diarrhoeal Disease Research, Bangladesh, on a cohort of adults and adolescents >11 years of age. A total of 614 individuals with presumptive pulmonary TB based on TB signs, symptoms and radiography are being recruited from 28 August 2023. Spot sputum is collected for standard reference testing (L-J culture, GeneXpert MTB/Rif, acid-fast Bacilli microscopy) to fine-tune categorisation of TB disease status for each participant, defined as (1) definite TB (at least one positive standard reference test); (2) probable TB (not microbiologically confirmed but under TB treatment); (3) possible TB (no TB treatment but signs, symptoms and radiography suggestive of TB); (4) other respiratory disease (microbiologically not confirmed and no radiography presenting abnormalities compatible with TB); and (5) unknown (no microbiological evidence with normal/no TB abnormalities with radiography). Urine and EBC specimens will be subjected to LAM POC testing and biobanked for further investigation. Statistical analyses will include an assessment of diagnostic accuracy by constructing receiver operating curves and calculating sensitivity and specificity, as well as post-test probabilities.Ethics and dissemination The study protocol was approved by the Research Review Committee as well as the Ethical Review Committee of icddr,b and recorded under a protocol reference number, PR-2301. Results will be submitted to open-access peer-reviewed journals, presented at academic meetings, and shared with national and international policymaking bodies.