Model estimates targeted tuberculosis case finding could improve efficiency in Malawi

Researchers used mathematical models to assess whether childhood Mycobacterium tuberculosis immunoreactivity surveys could guide active case finding in Blantyre, Malawi. The study covered 33 urban neighborhoods with an estimated population of 266,710. Annual infection risk estimates came from surveys of children under five attending primary care. A Markov microsimulation compared passive case finding alone with the addition of either untargeted or geographically targeted active case finding, estimating life expectancy, disability-adjusted life years (DALYs), and health-system and societal costs.

Targeted case finding covering half the population was estimated to identify 80% of individuals with TB. Its estimated cost per DALY averted was US$400 (95% credible interval, $20–$1,000), compared with $700 ($100–$1,500) for untargeted case finding. Compared with passive case finding alone, untargeted active case finding increased modeled life expectancy among people with TB disease by 3.3 years (95% credible interval, 1.7–5.4).

Although targeting improved efficiency, both approaches exceeded available cost-effectiveness thresholds for Malawi in the main analysis. Cost-effectiveness improved when models assumed higher TB prevalence or greater transmission reductions. These are modeled projections, not observed intervention effects, and depend on an uncertain relationship between childhood infection risk and neighborhood TB prevalence. The authors noted that lower-cost surveillance data collection would be needed for wider adoption.