Estimating Cost Functions for Resource Allocation Using Transmission Models: A Case Study of Tuberculosis Case Finding in South Africa.

OBJECTIVE: Cost functions linked to transmission dynamic models are commonly used to estimate the resources required for infectious disease policies. We present a conceptual and empirical approach for estimating these functions, allowing for nonconstant marginal costs. We aim to expand on the current approach which commonly assumes linearity of cost over scale. METHODS: We propose a theoretical framework adapted from the field of transport economics. We specify joint functions of production of services within a disease-specific program. We expand these functions to include qualitative insights of program expansion patterns. We present the difference in incremental total costs between an approach assuming constant unit costs and alternative approaches that assume economies of scale, scope and homogeneous or heterogeneous facility recruitment into the programme during scale-up. We illustrate the framework's application in tuberculosis, using secondary data from the literature and routine reporting systems in South Africa. RESULTS: Economies of capacity and scope substantially change cost estimates over time. Cost data requirements for the proposed approach included standardized and disaggregated unit costs (for a limited number of outputs) and information on the facilities network available to the program. CONCLUSIONS: The defined functional form will determine the magnitude and shape of costs when outputs and coverage are increasing. This in turn will impact resource allocation decisions. Infectious diseases modelers and economists should use transparent and empirically based cost models for analyses that inform resource allocation decisions. This framework describes a general approach for developing these models.

Perceived HIV stigma and HIV testing among men and women in rural Uganda: a population-based study.

BACKGROUND: Stigma is a formidable social structural barrier to HIV testing, and yet the effect of stigma on HIV testing is rarely examined at the community level. We aimed to examine the geospatial relationships of perceived HIV stigma and HIV testing among men and women living in rural Uganda. METHODS: Women and men (aged ≥18 years or emancipated minor) residing in rural areas of Uganda who self-identified as HIV negative completed interviews that included measures of HIV testing history and how participants perceived HIV stigma. We used geospatial cluster analyses to identify areas of higher perceived stigma and lower perceived stigma and the geographical dispersion of these areas. We used Poisson regression models stratified by gender to test individual-level and community-level perceived stigma in relation to frequency of HIV testing in the previous 2 years. FINDINGS: Between Nov 25, 2015, and May 26, 2017, we interviewed 9740 participants (4359 [45%] men and 5381 [55%] women]), among whom 940 (9%) had never been tested for HIV, and among those who had been tested, 1131 (12%) had not been tested in the previous 2 years. Men (3134 [72%] of 4359) were less likely to have been tested in the past 2 years than women (4535 [84%] of 5381) were (p<0·001). We used Poisson regression models, reporting B coefficients, to test study hypotheses regarding the effects of individual-level and community-level stigma on HIV testing frequency counts. Multilevel modelling showed that women showed significant individual-level (B=-0·173, p<0·001) and community-level (B=-0·223, p<0·001) associations between lower stigma predicting higher rates of HIV testing. For men, lower individual-level perceived stigma was also associated with higher testing frequency (B=-0·030, p=0·018), whereas higher community-level perceived stigma was associated with higher testing frequency (B=0·077, p=0·008). INTERPRETATION: Our results suggest that perceived HIV stigma at the community level exerts a differential influence on testing for women and men. HIV testing campaigns that are targeted to men and women in rural Uganda will require gender tailoring to fit local contexts. FUNDING: US National Institute of Mental Health.