OBJECTIVES: Household contact investigation (HCI) for tuberculosis (TB) is recommended but often constrained by resource availability. Many household contacts are unavailable during regular business hours, resulting in missed cases among high-risk individuals. As part of a randomized trial in South Africa, this study aimed to evaluate the cost-effectiveness of extending standard HCI (Mondays through Fridays, 8am-4pm) to non-routine hours.

METHODS: We performed an economic evaluation of standard HCI and two novel strategies: holiday-based HCI in a rural setting and off-peak HCI during weekends and evenings in an urban setting. Costs were derived from 2022 expenditure data, and secondary cases were defined as household contacts who were sputum culture positive. The incremental cost-effectiveness ratio (ICER) of each strategy was evaluated against no HCI from the health system perspective in 2022 US dollars. A country-specific willingness-to-pay threshold of $3,015 per disability-adjusted life year (DALY) averted was used. We evaluated uncertainty and drivers of cost-effectiveness using deterministic and probabilistic sensitivity analyses.

RESULTS: Relative to no HCI, standard HCI was estimated to cost $1,000 [95% Uncertainty Interval (UI): $710 - $1,500] per DALY averted in the urban setting and $2,900 [95% UI: $2,100 - $4,000] in the rural setting. Corresponding ICER estimates were $2,000 [95% UI: $1,300 - $3,200] per DALY averted for off-peak (urban) and $4,500 [95% UI: $2,800 - $6,300] for holiday (rural) HCI. Personnel costs, travel costs (in the rural setting), and TB prevalence among household contacts were primary drivers of cost-effectiveness.

CONCLUSIONS: Standard HCI for TB is likely cost-effective in urban and rural South Africa, though cost-effectiveness varies by setting and strategy. In urban settings, off-peak HCI may still be cost-effective for individuals unreachable during standard business hours. Long travel times and lower TB prevalence affect HCI cost-effectiveness in rural settings; these barriers may be overcome by integrating HCI for TB into broader home-based interventions.