As described in the main text, costs were developed through data on PPIA operating costs and interviews with implementing partners. See methods for more information on cost calculations. All costs are given in US dollars, and subject to variation within ±25% in the uncertainty analysis. See online supplemental table S2 in the supporting information for a further breakdown of these costs. Note that the PPIAs in Mumbai and Patna differed in several important respects, including the service delivery model and incentive structures employe, the provider profile and provider behaviour on test preferences, and health infrastructure availability (drugs and diagnosis). Consequently, any direct comparison between Mumbai and Patna costs should be performed with caution.

*A breakdown of provider engagement costs by provider type was not available in Mumbai; we therefore assumed the same costs per FQ and LTFQ provider. In practice, the cost of LTFQ engagement is generally expected to be lower than the cost stated here for FQs; our analysis is thus conservative by tending to overestimate the overall cost of private sector engagement.

FQ, formally qualified; LTFQ, less-than-fully-qualified; PPIA, Public–Private Interface Agencies.