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Background: Countries are currently progressing towards the elimination of new paediatric HIV infections by 2015. WHO published new consolidated guidelines in June 2013, which now recommend either ‘Antiretroviral drugs (ARVs) for women living with HIV during pregnancy and breastfeeding (Option B)’ or ‘Lifelong antiretroviral therapy (ART) for all pregnant and breastfeeding women living with HIV (Option B+)’, while de facto phasing out Option A. This study examined health outcomes and cost impact of the shift to WHO 2013 recommendations in Zambia. Methods: A decision analytic model was developed based on the national health system perspective. Estimated risk and number of cases of HIV transmission to infants and to serodiscordant partners, and proportions of HIV-infected pregnant women with CD4 count of ≤350 cells/mm3 to initiate ART were compared between 2010 Option A and the 2013 recommendations. Total costs of prevention of mother-to-child transmission of HIV (PMTCT) services per annual cohort of pregnant women, incremental cost-effectiveness ratio (ICER) per infection averted and quality-adjusted life-year (QALY) gained were examined. Results: Our analysis suggested that the shift from 2010 Option A to the 2013 guidelines would result in a 33% reduction of the risk of HIV transmission among exposed infants. The risk of transmission to serodiscordant partners for a period of 24 months would be reduced by 72% with ‘ARVs during pregnancy and breastfeeding’ and further reduced by 15% with ‘Lifelong ART’. The probability of HIV-infected pregnant women to initiate ART would increase by 80%. It was also suggested that while the shift would generate higher PMTCT costs, it would be cost-saving in the long term as it spares future treatment costs by preventing infections in infants and partners. Conclusion: The shift to the WHO 2013 guidelines in Zambia would positively impact health of family and save future costs related to care and treatment. © 2014 Ishikawa et al.
We developed a decision analytic model based on the national health system perspective and compared expected health outcomes and costs of 2010 Option A and 2013 guidelines: ARVs during pregnancy and breastfeeding (Option B) and Lifelong ART (Option B+) (Figure 1). The model started with an annual cohort of HIV-infected pregnant women in Zambia. In the model, it was assumed that all HIV-infected pregnant women were diagnosed HIV positive for the first time during the current pregnancy. Then as per 2010 Option A, CD4 assessment was provided and its results guided initiation of ART or ARV (ZDV) prophylaxis for women. In this analysis, CD4 cell count of ≤350 cells/mm3 represented the priority eligibility criterion for initiating ART. It was assumed that for those who could not access CD4 test and/or did not receive the results of the tests, ARV prophylaxis was provided. ARV prophylaxis for exposed infants was considered independently regardless of their mothers’ access to prophylaxis, since there had been cases of HIV-exposed infants identified for the first time after the delivery and started on prophylaxis. For ARVs during pregnancy and breastfeeding (Option B) and Lifelong ART (Option B+), triple ARV drugs were provided without CD4 assessment. We then estimated the probability of HIV transmission to exposed infants and to serodiscordant partners, and the probability of ART initiation for HIV-infected pregnant women with CD4 cell count ≤350 cells/mm3 for each option. TreeAge Pro 2012 (TreeAge Software, Inc.) was used for the development of the decision tree and the analysis. Model inputs used in this study are shown in Table 1. Probabilities of perinatal HIV transmission to infants were based on the estimates by UNAIDS reference group on estimates, modelling and projections [12]. Probabilities of transmission to serodiscordant partners were estimated based on available evidence including HPTN 052 study [8], [13], [14], [15], [16]. We assumed that maternal ARV prophylaxis for 2010 Option A did not reduce the risk of HIV transmission to serodiscordant partners. CD4 cell count distribution of HIV-infected pregnant women was based on the study by Carter and others [17]. Discordance rate (i.e. HIV positive female aged 15–49 with HIV negative partner) was estimated at 36.8% based on the national data [18]. It was assumed that HIV-infected pregnant women initiated ARV prophylaxis or ART from the 14th week of pregnancy and HIV-exposed infants were breastfed until 12 months of age. The time horizon for the analysis was from the first antenatal care to 18 months after delivery. In addition, a time horizon of 10 years was also applied when the long-term cost implication of treatment for infected children and serodiscordant partners was examined. Demographic data and programme inputs for PMTCT were based on the UN data, Zambia national report 2012, and field level data collected by the Zambia Ministry of Health – Japan International Cooperation Agency scaling up of quality HIV/AIDS care service management project (SHIMA) in collaboration with National Center for Global Health and Medicine (NCGM) [10], [19]. Costs of PMTCT services and HIV treatment were estimated using the Costing Tool for Elimination Initiatives (CTEI) developed by NCGM in collaboration with Asia-Pacific United Nations Task Force for the Prevention of Parents-to-Child Transmission of HIV and Pan American Health Organization, which estimates the costs and health outcomes of PMTCT interventions [20]. Costs of ARVs and laboratory tests including rapid HIV test were estimated based on the WHO Global Price Reporting Mechanism as well as on the Clinton Health Access Initiative (CHAI) price list [21], [22], [23]. Costs of health services were derived from the WHO Choosing Interventions that are Cost Effective (WHO-CHOICE) [24]. All costs were discounted at 3% annually. Costs of PMTCT included HIV testing for both pregnant women and their partners, ARVs, other necessary laboratory tests, and health care services. Treatment cost included the first line ARVs, laboratory monitoring, and health care services for out-patient clinic. Main outcomes of this study are divided into two categories, namely health related outcomes and cost related outcomes. In health related outcomes, expected risks and number of HIV transmission to infants at the age of 18 months, HIV transmission to serodiscordant partners, and ART initiation of HIV-infected pregnant women with CD4 cell count of ≤350 cells/mm3 were examined and compared among 2010 Option A, ARVs during pregnancy and breastfeeding (Option B), and Lifelong ART (Option B+). Estimated probabilities of transmission to infants and serodiscordant partners and ART initiation by the model were entered into the CTEI, which provided the estimated number of infections par annual cohort of pregnant women in Zambia. As for cost related outcomes, total costs of PMTCT services per annual cohort of pregnant women in the country as well as future treatment costs as a result of HIV transmission to infants and serodiscordant partners over a period of ten years were examined and compared among different options. Incremental cost-effectiveness ratio (ICER) with regards to infant and partner infections averted and quality-adjusted life-year (QALY) gained were calculated. In this study we applied 16.88 QALYs gained per infant infection averted [25] and 5.83 QALYs gained per partner infection averted [26] based on the past study. First, base-case analysis was conducted, in which we examined outcomes of each options under the current health service coverage and utilization in Zambia. Then we performed sensitivity analysis on key parameters in order to examine the robustness of our findings. Parameters including access and utilization of health services, discordance rate, and HIV prevalence were varied enhancing their possible range as well as the changes in the future (e.g. improvement in service coverage and reduction of HIV prevalence). Cost-effectiveness analysis was conducted, in which cost per infection averted and ICER per QALY gained were calculated. Based on the WHO’s guidance, we defined that ICER below the annual gross domestic product (GDP) per capita in the country as very cost-effective, and below the three times of GDP per capita as cost-effective [27].
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