Concurrent use of low complexity automated NAATs for TB diagnosis and detection of resistance: A cost-effectiveness analysis

Current TB diagnostics relying on respiratory samples are less effective in children (under 10 years), children living with HIV (CLHIV) and adult people living with HIV (PLHIV). Concurrent testing using low-complexity automated nucleic acid amplification tests (LC-aNAATs) on multiple sample types and Lateral Flow Lipoarabinomannan (LF-LAM) improves diagnostic performance, but concerns about cost-effectiveness remain. To inform WHO guideline development group (GDG) recommendation we developed stochastic decision analysis model to evaluate the cost-effectiveness of concurrent LC-aNAAT testing in these populations in Malawi and the Philippines. The analysis, conducted from a healthcare system perspective estimated incremental cost per disability-adjusted life year (DALY) averted using country-specific parameters from published literature and systematic review conducted for GDG. Concurrent testing was assessed using LC-aNAAT on respiratory and stool samples for children, LC-aNAAT on respiratory samples and LF-LAM for PLHIV, and a combination of both approaches for CLHIV. Concurrent testing in children compared to respiratory samples had incremental cost per DALY averted of $253 (95% uncertainty interval (UI): $123 to $2317) in Malawi and $156 (95% UI: $79 to $888) in the Philippines. For PLHIV, concurrent testing had an incremental cost per DALY averted of $42 (95% UI: $18 to $345) in Malawi and $28 (95% UI: $12 to $249) in the Philippines. In CLHIV, concurrent testing had an incremental cost per DALY averted of $43 (95% UI: $28 to $89) in Malawi and $29 (95% UI: $18 to $63) in the Philippines. Sensitivity analyses highlighted TB prevalence and respiratory sample availability as key influencers of cost-effectiveness. In scenarios with higher TB prevalence, cost-effectiveness improved, while an increase in the probability of producing respiratory sample resulted in worsening cost-effectiveness estimates. Concurrent use of LC-aNAATs on multiple sample types and in conjunction with LF-LAM emerged as highly cost-effective strategy for diagnosing TB among children, PLHIV, and CLHIV.