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

Abstract 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. Summary What is already known? WHO guidelines recommend systematic screening for Tuberculosis at health facilities in high-burden settings, but implementation is challenging. Care cascades have been widely used by HIV programmes to evaluate care delivery but have only recently been applied to TB care. Care cascades help to define the steps of the cascade most in need of intervention What are the new findings? In this study, only 8.2% of those clinically indicated to test for TB (as per national guidelines in Malawi) did so, with patients lost at every step of the diagnosis care cascade. Failure to request sputum by clinicians despite elicited symptoms led to the biggest single gap in the diagnosis care cascade, followed by not asking about symptoms. If all patients attending the clinic were screened for TB as per the guidelines, the current testing facilities would only be able to process up to two thirds of the required samples. What do the new findings imply? Interventions focusing on health worker behaviour may have the greatest potential for retaining presumptive TB patients within the diagnosis cascade We must formalise and strengthen reporting on the early steps in the TB care cascade: a requirement to report numbers of screened presumptive TB cases would allow greater focus on these critical steps. If identification of presumptive TB patients is subsequently improved a novel high-throughput approach to triage testing using new diagnostics will be required for LMICs to increase capacity.