# Cost-benefit analysis of the prevention of mother-to-child transmission of HIV | infectious diseases of poverty

### study design

For the societal perspective of the study, all PMTCT costs were considered, regardless of who paid for them. Based on the results of the pilot survey, the funding channels of the PMTCT of HIV included the Chinese central government, the Sichuan provincial government, the Liangshan prefectural government, the county governments, MCHs, non-governmental organizations (NGOs) and also individuals. Expenditure was made in MCHs, CDCs, general hospitals and by individuals. All costs were collected from the above institutions and individuals through two different types of questionnaires.

To collect the cost of PMTCT from HIV and efficacy data in 2017, the study was conducted from December 2018 to January 2019. Based on high, intermediate, and low HIV prevalence rates, the annual reported prevalence rates of HIV-positive pregnant women in the 17 counties of Liangshan Prefecture were 0.5–3.2%, 0.1–0.4%, and 0, respectively .0-0.1%. For each prevalence level, two counties were sampled based on purpose sampling to collect cost data from MCHs, CDCs, and general hospitals.

To collect individual costs, HIV-positive pregnant women registered in the PMTCT’s National Information System for HIV, Syphilis and HBV were sequentially recruited to the local clinic for a questionnaire survey. Individual costs included meals due to hospital visits, transportation due to hospital visits, infant formula, hospitalization, and medical expenses during pregnancy and labor. The loss of daily income due to hospital visits was not taken into account given the low daily income of Liangshan residents. The total individual costs in Liangshan were calculated by multiplying the average individual costs from the survey by the sample weight.

To estimate the sample size, the individual indirect costs as standard deviation (σ) were set at $74. 1, the allowable error (δ) was set at$14.8, and ({mu }_{alpha })((alpha=0.05)) was 1.96. The above parameters for sample size calculation were estimated based on local consumption levels. The formula used to calculate the sample size was as follows:

$$n={left(frac{{u}_{alpha }sigma }{delta }right)}^{2},$$

the estimated minimum sample size of HIV-positive pregnant women (n) was received as 96.

The sample size criterion for the pharmacoeconomic evaluation was mentioned as another method for estimating the sample size. The criterion suggested that the minimum sample size of each group for a high-quality pharmacoeconomic evaluation study should be no less than 100 cases [15].

### calculation

The costs were divided into three parts according to their traceability: direct medical costs, direct non-medical costs and indirect costs. Direct medical expenses covered the cost of drugs for ART and prophylaxis, EID of HIV, reagents for preliminary HIV screening tests, reagents for HIV re-inspection tests, laboratory consumables, hospital stay and laboratory equipment. Direct non-medical costs covered the salaries of those providing intervention services; individual transportation, individual meals, infant formula; and financial support for pregnant women. Indirect costs included staff training expenses, propaganda expenses, office expenses, and office equipment expenses.

According to China Accounting Standard No. 3 – Fixed Assets, the useful life has been set at 15 years for office furniture, 10 years for laboratory equipment, 6 years for office equipment and 5 years each for micropipettes. The scrap value rate was set at 0% for the micropipette and at 5% for other fixed assets [16]. The annual depreciation of fixed assets was determined using the straight-line method:

$$Annual , Depreciation = Cost , of , Asset* , left( {{1 }{-}Scrap , Value , Rate} right)/Useful , Life.$$

### profitability analysis

#### effectiveness analysis

In this study, the number of pregnant women tested for HIV (N1) and the number of HIV-positive pregnant women (N2) have been analyzed. To calculate the number of pediatric infections that their mothers’ HIV infection avoided (N3), N2 was multiplied by the difference between the rate (34.8%) with no intervention in China and the current rate (9.0%). The formula for calculation N3 was as follows:

$$N_{3} = N_{2} *(34.8 – 9.0% ).,$$

#### Health Utility Analysis

The years of life gained (LYs). N3 were calculated as a measure of health benefit using a mortality table. Reference was made here to 76.9 years – the life expectancy of people in Sichuan province in 2017 and the age-specific mortality rate from China’s sixth census [17]. The cost-benefit ratio (CUR) was used to measure the cost per LY gained as follows:

Where C was the cost of PMTCT, and u was the number of LYs gained N3.

#### Cost-benefit analysis

The benefits of PMTCT were of two types: direct benefits and indirect benefits. Direct benefit was defined as saving on the cost of ART N3, and it was computed based on a Markov model using the statistical software package heemod R-4.1.1 (WN Venables, DM Smith and the R Core Team). To create the Markov model, the disease process of HIV/AIDS was assumed to have the following health states: HIV state, AIDS state, and the absorbing state of death. It was also assumed that the life expectancy of mothers’ HIV-infected children was 25 years according to the literature [18], and that the cycle length of the Markov model was one year. The costs after 2017 were discounted at an annual rate of 3% to 2017 (Fig. 1).

The indirect benefit, defined as the economic value created by averted pediatric infections, was calculated by multiplying the estimated LYs by the age-weighted productivity GDP per capita, based on the human capital theory. The age-weighted productivity of 0-14, 15-44, 45-59 and over 60 year olds is 0.15, 0.75, 0.8 and 0.1, respectively [27].

The benefit-cost ratio (BCR), defined as the ratio of net output to economic input, was considered as the total net benefit per cost of PMTCT. It was calculated as follows:

$$BCR=frac{sum b}{sum c}=frac{sum left(Direct Benefit+No Direct Benefitright)-Cost of PMTCT}{Cost of PMTCT}.$$

### BCR sensitivity analysis

A one-way sensitivity analysis was performed for key variables to which BCRs were expected to be sensitive. It was assumed that the cost of PMTCT could vary by ±25%. The range of transition probabilities and costs of ART in the Markov model was between the lower and upper in Table 1, while the life expectancy of prevented pediatric infections ranged from 15 to 35 years and the discount rate ranged from 0 to 10%. Life expectancy in Liangshan ranged from 60 to 85 years, and GDP per capita ranged from USD 1295.8 to USD 8393.9 (Table 2).