Tuberculosis diagnosis cascade in Blantyre, Malawi: a prospective cohort study

Background Tuberculosis (TB) control relies on early diagnosis and treatment. International guidelines recommend systematic TB screening at health facilities in high-burden settings, but implementation is challenging. To construct a TB diagnosis care cascade, we investigated screening guideline adherence and completion of TB testing steps in Blantyre, Malawi. Methods A prospective cohort recruited adult (≥18) outpatients attending Bangwe acute-care primary clinic between 21/5/2018 and 6/9/2018. Entry interviews recording TB symptoms and demographic characteristics were linked to exit interviews by biometrics. Care cascades were constructed to estimate the proportion of patients progressing through each step of the diagnostic pathway. Multivariable logistic regression was used to investigate factors associated with being asked to submit sputum. Results Of 5,442 clinic attendances 2,397 (44%) had exit interviews. In clinically indicated participants (n=330) 203 (61.5%) were asked about cough, 39 (11.8%) were asked for sputum, 27 (8.2%) gave sputum and 1 (0.3%) received same-day results. Significant associations with request for sputum were: any TB symptom (aOR:3.20, 95%CI:2.02-5.06), increasing age (aOR:1.02, 95%CI:1.01-1.04 per year) and for HIV-negative participants only, a history of previous TB (aOR:3.37, 95%CI:1.45-7.81). Numbers requiring sputum survey (20/day) outnumbered diagnostic capacity (8-12/day). Conclusion Patients were lost at every stage of the TB care cascade, with same day sputum submission achieved in only 8.2% if clinically indicated. Infection control strategies should be implemented, with reporting on early steps of the TB care cascade formalised. High-throughput interventions, such as digital CXR, that can optimise same-day TB screening are urgently needed to meet WHO End TB goals.