Cost-effectiveness of strategies to reduce mother-to-child HIV transmission in Mexico, a lowprevalence

Transcription

1 Cost-effectiveness of strategies to reduce mother-to-child HIV transmission in Mexico, a lowprevalence setting Rely K, Bertozzi S M, Avila-Figueroa C, Guijarro M T Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology Five strategies (each considering two alternative treatments) for the prevention of mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) were evaluated. Strategy I (the status quo strategy) assumed that 4% of pregnant women would receive prenatal voluntary counselling and testing (VCT) for HIV, and that either a long-course, three-phase treatment with zidovudine (ZDV) or a shortcourse intrapartum treatment with nevirapine (NVP) would be offered to those who were eligible. Elective Caesarean would be performed in some cases and breast-feeding substitution would also be offered. Strategy II was identical to strategy I, except that VCT was increased from 4 to 85%. Strategy III administered a questionnaire to 85% of pregnant women and offered VCT to the 30% identified as being at highest risk, with the same treatment as strategies I and II. Strategy IV was the same as strategy II, except that group counselling was used prior to testing and only those women identified as HIV-positive received individual post-test counselling. Strategy V was the same as strategy IV, with an additional 15% of women who arrived for delivery without VCT being offered HIV rapid testing, and treatment if HIV-positive. ZDV would be administered in accordance with the ACTG 076 protocol. Under this protocol, treatment starts with 100 mg oral ZDV five times a day between the 14th and 34th week of gestation, until labour begins. Intravenous ZDV (2 mg/kg) is then given during labour as a loading dose, followed by a continuous infusion of 1 mg/kg per hour until delivery. Finally, the infant is given ZDV syrup (2 mg/kg) every 6 hours, starting 8 to 12 hours after birth and continuing for 6 weeks). NVP would be given as one 2-mg oral dose to mothers at the onset of labour, followed by a 2-mg/kg oral dose given to their babies within 3 days of birth. Type of intervention Primary prevention (of child infection). Economic study type Cost-effectiveness analysis. Study population The study population comprised pregnant women in Mexico's public health care system. Setting The setting was secondary and tertiary care. The study was performed in Mexico. Page: 1 / 7

2 Dates to which data relate The effectiveness and resource use data were gathered from undated personal correspondence, and from studies published between 1991 and The cost data were taken from undated personal correspondence and from studies published between 1994 and 1998, and were adjusted to 2001 prices. Source of effectiveness data The estimates for the final outcomes were based on the non-systematic use of published studies, expert opinion and the authors' assumptions. The data were obtained from Mexico-specific sources when available. Modelling A spreadsheet model was used to estimate the costs and benefits of each strategy. Other details were not provided, but a full description of the model has been published elsewhere (Bollinger et al., see Other Publications of Related Interest). Outcomes assessed in the review The authors did not describe how they identified the studies that provided the values of the model parameters. The parameters obtained from published studies and used in the model were: HIV-positive women who received prenatal care and are eligible for ZDV treatment; HIV-positive women who accepted ZDV treatment; HIV-negative women who changed their risk behaviour after counselling; HIV prevalence among pregnant women in Mexico; the vertical transmission probabilities by type of treatment (ZDV, NVP, or none), delivery (vaginal or Caesarean) and feeding (bottle, breastfeeding, or a combination of formula and breastfeeding); the treatment efficacy of ZDV; and the treatment efficacy of NVP. Study designs and other criteria for inclusion in the review Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included The values for the parameters in the model were obtained from at least 9 published studies and reports. Page: 2 / 7

3 Methods of combining primary studies Investigation of differences between primary studies Results of the review The following values were used in the model: HIV-positive women who received prenatal care and were eligible for ZDV treatment, 61%; HIV-positive women who accepted ZDV treatment, 75%; HIV-negative women who changed their risk behaviour after counselling, 0% (range: 0-80); HIV prevalence among pregnant women in Mexico, 0.09%; the vertical transmission probabilities with ZDV treatment were with formula, with breastfeeding, and with a combination of formula and breastfeeding when delivery was vaginal, and (formula), (breastfeeding) and (combination), respectively, when delivery was by Caesarean; the vertical transmission probabilities with NVP treatment were with formula, with breastfeeding, and with a combination of formula and breastfeeding when delivery was vaginal, and (formula), (breastfeeding) and (combination), respectively, when delivery was by Caesarean; the vertical transmission probabilities without treatment were with formula, with breastfeeding, and with a combination of formula and breastfeeding when delivery was vaginal, and (formula), (breast) and (combination), respectively, when delivery was by Caesarean; the treatment efficacy of ZDV, 67%; the treatment efficacy of NVP, 50%. Methods used to derive estimates of effectiveness Values for other parameters used in the model were based on authors' assumptions and, in one case, expert opinion. Estimates of effectiveness and key assumptions The authors made the following assumptions: 100% of HIV-positive women with an attended delivery in a health facility were eligible for NVP treatment; 75% of HIV-positive women eligible for ZDV are offered this treatment; the proportion of HIV-positive women who are eligible for ZDV but who do not receive it and are offered NVP treatment is 90%; 90% of HIV-positive women accept NVP treatment; 70% of HIV-positive women comply with the ZDV treatment regimen; 95% of HIV-positive women comply with the NVP treatment regimen; Page: 3 / 7

4 50% of HIV-positive women undergo elective Caesarean; and less than 2% of HIV-positive women who receive prenatal care and ARV (not defined) treatment go on to breastfeed their infant. Measure of benefits used in the economic analysis The measure of health benefit used was the number of child deaths averted. The number of child infections averted and the number of adult infections averted were also reported. These measures of benefits appear to have been obtained by modelling. Direct costs Only the direct costs to the health service were considered. These included VCT, long-course ZDV treatment regimen, NVP treatment regimen, elective Caesarean, formula milk, and the lifetime costs of treating paediatric and adult HIV or AIDS. Capital costs were specifically excluded on the basis that only the additional costs of existing health care services were considered. Moreover, the costs of health provider time for drug administration were also excluded, as the authors estimated these to be minimal. The spreadsheet model was populated with cost data taken from personal communications and published sources, and from some authors' assumptions. The costs were adjusted to 2001 prices, although the method used was not reported. The lifetime treatment costs were calculated by assuming 7 years' survival for children and 10 years' survival for adults, and were discounted at 5%. The direct costs estimated were total costs. Statistical analysis of costs No statistical analysis of the costs was reported. Indirect Costs The indirect costs were not included, which was appropriate given the stated study perspective. Currency US dollars ($). Sensitivity analysis One-way simple sensitivity analyses were carried out on all input parameters to investigate variability in the data. The authors did not justify the ranges over which the variables were tested, nor did they report all of the ranges considered. Estimated benefits used in the economic analysis With ZDV, 4 child deaths were averted by strategy I, 79 by strategy II, 40 by strategy III, 79 by strategy IV and 89 by strategy V. With NVP, 3 child deaths were averted by strategy I, 56 by strategy II, 28 by strategy III, 56 by strategy IV, and 63 by strategy V. With ZDV, 4 child infections were averted by strategy I, 91 by strategy II, 46 by strategy III, 91 by strategy IV and 102 by strategy V. With NVP, 3 child infections were averted by strategy I, 64 by strategy II, 32 by strategy III, 64 by strategy IV and 72 by strategy V. Cost results Page: 4 / 7

5 When ZDV was used, the total cost of treatment was $268,359 for strategy I, $5,723,943 for strategy II, $1,804,155 for strategy III, $3,800,039 for strategy IV and $4,336,690 for strategy V. When NVP was used, the total cost of treatment was $259,262 for strategy I, $5,524,724 for strategy II, $1,704,545 for strategy III, $3,600,820 for strategy IV and $4,113,507 for strategy V. Synthesis of costs and benefits Cost-effectiveness ratios were calculated as the cost per child death prevented. For ZDV treatment, strategies III, IV and V were all more cost-effective than strategy I. In the baseline case, the cost per child death prevented was $54,535 compared with $ for strategy III, $28,098 for strategy IV and $28,991 for strategy V. Strategy II was dominated as it was more expensive and less effective than the other strategies. For treatment with NVP, strategies III, IV and V were all more cost-effective than strategy I. In the baseline case, the cost per child death averted was $80,923 compared with $41,679 for strategy III, $43,098 for strategy IV and $44,367 for strategy V, with strategy II again dominated. NVP was less cost-effective than ZDV for any of the five strategies. An incremental analysis was used to compare strategies IV and V. The incremental cost per child death averted with strategy V, compared with strategy IV, was $36,423 for ZDV treatment and $54,918 for NVP treatment. The authors also reported the cost per child infection prevented for some of the compared strategies. They stated that the incremental cost per child infection averted was significantly higher for strategy IV than for strategy V, but was lower than that for strategies I or II. It was difficult to identify whether the results were sensitive to modifications in the model parameters, as the results of the sensitivity analyses were given as the cost per child infection averted and not as the cost per child death avoided. Authors' conclusions In low-prevalence settings such as Mexico, the main cost-driver in programmes to decrease mother-to-child transmission (MTCT) of human immunodeficiency virus (HIV) was the cost of voluntary counselling and testing (VCT). Even the most cost-effective strategy (i.e. strategy III) was at best only marginally cost-effective compared with other interventions to reduce infant or child mortality, suggesting that the implementation of such an intervention should be questioned. CRD COMMENTARY - Selection of comparators A justification was given for the alternative strategies used. They reflected the range of options under consideration by the Mexican government for MTCT prevention of HIV or AIDS. You should decide if these are representative of diagnosis and treatment strategies for this disease in your own setting. The authors commented that two alternative short courses of ZDV were also assessed initially, but the results were not reported in the study as they were more expensive and appeared to be no more effective than NVP. Validity of estimate of measure of effectiveness A systematic review of the literature was not undertaken. Although this is common practice with models, it does not always ensure that the best data available are used in the model. The authors appear to have used data from the available studies selectively. In addition, they did not consider the impact of differences between the studies identified when estimating the effectiveness. More than half of the estimates of effectiveness were assumptions made by the authors, without any justification for the choice provided. The authors reported that the assumption that therapy was completely ineffective for those women who did not comply fully might have resulted in an underestimation of the effectiveness of the interventions. Although the estimates were investigated in a sensitivity analysis, it was unclear how the authors chose the ranges used. The study would have been improved had a systematic review of the literature been carried out to identify the value of input parameters, as a major weakness of the study was the lack of evidence supporting some of the values used as input parameters in the model. Page: 5 / 7

6 Validity of estimate of measure of benefit The summary measure of benefit was the number of child infections prevented, and this was modelled. The principal input parameters for the model were derived from an ad hoc review, expert opinion and the authors' assumptions, which might have biased the results of the health benefit measures obtained. Therefore, the quality of the input parameters is a limiting feature of the study. The summary measure of benefit considered was appropriate for the type of intervention under analysis, although the estimation of the number of quality-adjusted life-years gained would have enabled comparisons with different interventions. Validity of estimate of costs The cost analysis was performed from the perspective of the government as the decision-maker. Only the direct costs to the health service were included. It appears that all the relevant categories of costs have been included in the analysis. The resource quantities and the costs were not reported separately, which will limit the reproducibility of the study in other settings. The authors used published sources, expert opinion and their own assumptions for the estimation of costs, and it was unclear whether the values used for some of the costs were appropriate. The costs were treated deterministically, and sensitivity analyses were conducted to assess the robustness of the estimates when the estimated costs were modified. The ranges used were not justified, and it was not possible to determine whether they were appropriate. Discounting was applied to the lifetime costs of HIV treatment. It appears that costs, rather than charges, have been reported, which would reflect the true opportunity costs of the interventions studied. The authors reported that the costs were adjusted to a single price year. Other issues The authors made limited comparisons of their findings with those from other studies, so it is not known how far their results agree with other published results. In terms of the generalisability of the results to other settings, the authors commented that the decision to implement the proposed strategies would differ across different settings since the costeffectiveness of the interventions would vary according to the different health care systems found in Mexico. The authors compared their findings with those from programmes in Africa, which has a high maternal prevalence of HIV. In an attempt to be consistent with similar studies, the authors selected the cost per child death averted as the costeffectiveness ratio used in the economic evaluation. The authors appear to have presented their results selectively since the results of the sensitivity analyses were reported as the cost per child infection prevented, and not as the cost per child death prevented. Implications of the study The authors stated that pilot studies should be undertaken to validate and cost these results before they are used to inform large-scale policy decisions. Four areas for further research were defined: more precise estimates of the prevalence of maternal HIV; more precise costs of VCT options; additional approaches to reducing the cost of VCT; and the current cost of caring for children with HIV. Source of funding None stated. Bibliographic details Rely K, Bertozzi S M, Avila-Figueroa C, Guijarro M T. Cost-effectiveness of strategies to reduce mother-to-child HIV transmission in Mexico, a low-prevalence setting. Health Policy and Planning 2003; 18(3): Page: 6 / 7

7 Powered by TCPDF ( PubMedID Other publications of related interest Bollinger L, Stover J. Decision model for evaluating strategies to prevent mother-to-child transmission of HIV. Washington (DC): The Futures Group International, PASCA; Indexing Status Subject indexing assigned by NLM MeSH AIDS Serodiagnosis /economics; Anti-HIV Agents /administration & dosage /economics; Breast Feeding; Cesarean Section /economics; Cost of Illness; Cost-Benefit Analysis; Counseling /economics; Female; HIV Infections /economics /epidemiology /prevention & control /transmission; Humans; Infant, Newborn; Infectious Disease Transmission, Vertical /economics /prevention & control; Mexico /epidemiology; Nevirapine /administration & dosage /economics; Pregnancy; Pregnancy Complications, Infectious /economics /epidemiology /prevention & control; Prenatal Care /economics /methods; Value of Life /economics; Zidovudine /administration & dosage /economics AccessionNumber Date bibliographic record published 31/08/2005 Date abstract record published 31/08/2005 Page: 7 / 7