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State AIDS drug assistance programs: equity and efficiency in an era of rapidly changing treatment standards |
Johri M, Paltiel A D, Goldie S J, Freedberg K A |
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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 Several alternative programmes to assist human immunodeficiency virus (HIV)-infected persons who are uninsured, or have limited resources, were examined. In the USA there were 54 state AIDS Drug Assistance Programs (ADAPs). These differed in their formulary and access policies, geographic region, and state and HIV-infected population sizes. In the current analysis, the programmes were aggregated in 11 types, corresponding to 11 states. The programmes were denoted by US Postal Service state abbreviations (i.e. AR, FL, GA, MS, MO, NE, OK, OR, NV, SD, TX). Each state programme was modelled at three points in time, representing the fiscal years 1997, 1998 and 1999. Therefore, 33 alternative strategies were considered. The programmes were evaluated according to two aspects, the opportunistic infection (OI) prophylaxis strategy and the antiretroviral strategy.
Type of intervention Treatment and secondary prevention.
Study population The study population comprised a hypothetical cohort of HIV-infected patients.
Setting The setting was primary and secondary care. The economic study was conducted in the USA.
Dates to which data relate The effectiveness evidence came from studies published between 1995 and 2000. Resource use data referred mainly to 1991 and 1992. The price year was 1999.
Source of effectiveness data The effectiveness evidence was derived from a review of completed studies.
Modelling A state transition model was used to analyse the natural history, treatment efficacy, and lifetime costs of HIV infection. The Cost-Effectiveness of Preventing AIDS Complications (CEPAC) model had been published already. The model used Monte Carlo simulations to follow the clinical course of a cohort of 1 million patients from time of entry to the model until death under a variety of scenarios. The scenarios represented different ADAP policies for the administration of antiretroviral therapies and OI prophylaxis. The typical patient was 33 years of age and 80% of the patients were men.
The model defined a series of health states that were predictive of patient health status, clinical prognosis, resource consumption, and quality of life. These health states fell into three main categories (chronic, acute, and death). The chronic and acute health states were segmented along a number of dimensions, which corresponded to features of clinical interest. For example, CD4 cell count, HIV RNA, history of clinical complications, time since initiation of highly active antiretroviral therapy (HAART), and prophylaxis again specific OIs. Progression of HIV disease, risks of clinical events, treatment effects, and resource consumption were linked to both CD4 cell count and HIV RNA. The cycle length was 1 month and the time horizon was the lifetime of the patient.
Outcomes assessed in the review The outcomes assessed were the natural history of AIDS and efficacy data for HAART.
Study designs and other criteria for inclusion in the review It was unclear whether a systematic review of the literature was conducted. The evidence concerning HAART efficacy came from randomised studies.
Sources searched to identify primary studies Criteria used to ensure the validity of primary studies The validity of the primary studies was ensured by the study design (randomised clinical trials).
Methods used to judge relevance and validity, and for extracting data Number of primary studies included The clinical evidence on HAART efficacy was derived from 7 primary studies. A single study provided data on the natural history of acquired immunodeficiency syndrome (AIDS).
Methods of combining primary studies Investigation of differences between primary studies Results of the review The results of the review were not reported.
Measure of benefits used in the economic analysis The summary benefit measure used was the gain in quality-adjusted life-years (QALYs), which were estimated using the model. The utility values used to calculate the QALYs were derived from patients participating in four AIDS Clinical Trials Group Protocols. The responses were transformed to approximate time trade-off utilities. An annual discount rate of 3%, as recommended in the USA, was applied to the QALYs.
Direct costs An annual discount rate of 3% was used as the lifetime costs were estimated. The unit costs were not presented separately from the quantities of resources used. The health services included in the economic evaluation were drugs, diagnosis and testing, and patient care across a variety of medical settings. In the model, each patient developing an acute complication received appropriate treatment regardless of its availability via the ADAP. The cost/resource boundary of the payer of direct costs was adopted. Resource use was mainly derived from a national survey for HIV-infected persons receiving health care services, the AIDS Cost and Service Utilization Study (ACSUS). The costs were derived from wholesale prices for drugs, hospital accounting systems for testing costs, and the ACSUS. A cost-to-charge ratio was applied to assess the true economic costs. All the costs were presented in 1999 values and were adjusted, when appropriate, using the medical care component of the Consumer Price Index.
Statistical analysis of costs The costs were treated deterministically in the base-case.
Indirect Costs The indirect costs were not considered.
Sensitivity analysis The results were presented under two main scenarios, depending on the high and low efficacy of HAART. Alternative values were derived from clinical trials. One-way sensitivity analyses were also conducted to assess the robustness of the estimated cost-effectiveness ratios to variations in several parameters. The variables investigated were medication costs (halving or doubling drug costs), health of the starting cohort (mean CD4 cell count of 250 or 350 cells/microL), quality of life adjustments, discounting, and choice of the comparator programme (using no programme as the comparator).
Estimated benefits used in the economic analysis Under the high-efficacy scenario, the QALYs were:
5.30 with AR97 and OR97;
5.61 with NV97, SD97, SD98, SD99, MS97 and AR98;
7.08 with GA97 and NE98;
7.38 with FL97, OK97 OK98, MS98, OR98, MO97, MO98 and NE97;
7.37 with TX97 and TX98;
9.23 with GA98, GA99 and NE99;
9.55 with OK99, NV98 and NV99; and
9.56 with AR99, MS99, TX99, OR99, MO99, FL98, FL99.
Under the low-efficacy scenario, the QALYs were:
4.69 with AR97 and OR97;
4.98 with NV97;
4.99 with AR98, SD97, SD98, SD99 and MS97;
5.70 with GA97, GA98, GA99, NE98 and NE99;
6.00 with NV98, NV99, MS99, NE97 and TX99;
6.01 with AR99, MS98, TX97, TX98, and FL99; and
6.02 with FL97, OK97, OK98, OK99, OR98, OR99, MO97, MO98, MO99 and FL98.
Cost results Under the high-efficacy scenario, the lifetime costs were:
$77,800 with AR97 and OR97;
$80,100 with NV97, SD97, SD98 and SD99;
$80,200 with MS97 and AR98;
$119,400 with GA97 and NE98;
$122,100 with FL97, OK97, OK98, MS98, OR98, MO97, MO98, TX97 and TX98;
$122,800 with NE97;
$145,500 with GA98, GA99 and NE99;
$148,800 with OK99, NV98 and NV99; and
$149,000 with AR99, MS99, TX99, OR99, MO99, FL98, FL99.
Under the low-efficacy scenario, the lifetime costs were:
$81,200 with AR97 and OR97;
$83,400 with NV97;
$83,500 with AR98, SD97, SD98 and SD99;
$83,600 with MS97;
$109,700 with GA97, GA98, GA99, NE98 and NE99;
$$112,500 with NV98, NV99, MS99, NE97, TX99 and AR99;
$112,600 with FL97, OK97, OK98, OK99, TX97, TX98 and FL99; and
$112,700 OR98, OR99, MO97, MO98, MO99 and FL98.
Synthesis of costs and benefits An incremental cost-effectiveness analysis was conducted to combine the costs and benefits of the alternative programmes. Only non-dominated results are reported here.
Under the high-efficacy scenario, the incremental cost per QALY over the next less costly strategy was $7,000 with MS97, $17,000 with OK99, and $25,000 with OR99, MO99, FL98 and FL99.
Under the low-efficacy scenario, the incremental cost per QALY over the less costly strategy was $7,000 with NV97, 13,000 with SD97, SD98 and SD99, and $28,000 with FL97, OK97, OK98, and OK99.
No strategy without several agents for prophylaxis of Pneumocystis carinii pneumonia and some for prophylaxis of Mycobacterium avium complex was efficient.
HAART was the main cost and survival driver.
The sensitivity analysis showed that the estimated cost-effectiveness ratios were sensitive to variations in medication costs (higher costs led to higher cost-effectiveness ratios). Minor changes were observed when other model inputs (e.g. quality of life weights, discounting and choice of comparator programme) were varied. In no case did the cost per QALY exceed the threshold of $50,000.
The authors stated that the policy results did not vary when alternative cost structures were considered.
Authors' conclusions The more comprehensive programme led to improvements in quality- adjusted life-years (QALYs) in comparison with more restrictive AIDS Drug Assistance Programs (ADAPs), but also to increased costs. Less efficient programmes could reach a more acceptable cost-effectiveness ratios by providing more prophylactic drugs for opportunistic infections (OIs), such as Pneumocystis carinii pneumonia and Mycobacterium avium complex. Overall, the implementation of ADAPs constituted a cost-effective use of care resources for human immunodeficiency virus (HIV).
CRD COMMENTARY - Selection of comparators The rationale for the selection of the comparators was clear since all possible ADAPs implanted across USA were considered. However, the content of each programme was unclear. The strategy of no programme was also included in the sensitivity analysis. Although this was not an available option in the USA, it could be the standard approach in other countries. You should decide whether they are valid comparators in your own setting.
Validity of estimate of measure of effectiveness The analysis of effectiveness used data derived from the literature, but it was unclear whether a systematic review of the literature was undertaken. The design of the primary studies, all of which were randomised trials, ensured the validity of the sources used. However, there was limited information on the study samples, and it was unclear how the primary estimates were extracted and their results combined. The results of the review were not reported. Uncertain aspects were investigated in the sensitivity analysis.
Validity of estimate of measure of benefit QALYs were used as the summary benefit measure. This choice was appropriate as it allowed the impact of the interventions on patient survival and quality of life to be assessed. Appropriate discounting, as recommended in the USA, was conducted. The impact of varying not only the discount rate, but also the utility values, was investigated in the sensitivity analysis. The source of the utility data was reported, as were the methods used to derive the utility weights. The authors noted that the utility weights were derived from a sample of patients, although the use of values elicited by means of validated measures (e.g. the SF-36) would have been more appropriate. QALYs can be compared with the benefits of other health care interventions.
Validity of estimate of costs The authors stated explicitly which perspective was adopted in the study. As such, it appears that all the categories of costs relevant to this perspective have been included in the analysis. Limited information on resource usage and the unit costs was provided, which limits the possibility of replicating the study in other settings. The source of data was provided and a cost-to-charge data was applied to determine the true economic costs of the interventions. No statistical tests were conducted on the costs, but extensive sensitivity analyses considering alternative cost structures were conducted. The price year was reported, which will facilitate reflation exercises in other settings.
Other issues The authors stated that their findings differed from some observational studies that had reported decreases in the total HIV care costs. However, the authors noted that such studies had a limited time horizon, while some evidence had suggested that the costs tended to increase over time. The results in terms of cost-effectiveness were comparable with two recently published studies on HAART in publicly funded health care systems. The authors acknowledged that the conclusions of the analysis relied strongly on the modelling approach, which was a simplification of HIV natural history.
Implications of the study The authors highlighted that future research should focus not only on efficiency but also on equity issues such as access criteria. The results of the current analysis should be considered within a national policy context, taking other policy dimensions potentially affecting the quality of the ADAP into consideration.
Source of funding Supported by the Centers for Disease Control and Prevention (Cooperative Agreement U643/CCU 114927); the National Institute of Allergy and Infectious Diseases via grant RO1-A142006 to the Cost-Effectiveness of Preventing AIDS Complications (CEPAC) project and CFAR grant 1P30A14285101A2; the Adult AIDS Clinical Trials Group of the National Institute of Allergy and Infectious Diseases (Cooperative Agreement U01 A138838); the Societal Institute for the Mathematical Sciences via grant DA 09531 from the National Institute on Drug Abuse; and the National Institute on Mental Health via grant MH56826 to the Yale Center for Interdisciplinary Research on AIDS.
Bibliographic details Johri M, Paltiel A D, Goldie S J, Freedberg K A. State AIDS drug assistance programs: equity and efficiency in an era of rapidly changing treatment standards. Medical Care 2002; 41(5): 429-441 Other publications of related interest Hammer SM, Katzenstein DA, Hughes MD, et al. A trial comparing monotherapy with combination therapy in HIV-infected adults with CD4 cell counts from 200 to 500 per cubic millimetre. AIDS Clinical Trial Group Study 174 Study Team. New England Journal of Medicine 1996;335:1081-90.
Indexing Status Subject indexing assigned by NLM MeSH Acquired Immunodeficiency Syndrome /drug therapy /blood /economics /mortality /psychology; Anti-HIV Agents /economics; CD4 Lymphocyte Count; Comparative Study; Cost of Illness; Cost-Benefit Analysis; Direct Service Costs /statistics & Disease Progression; Efficiency, Organizational; Eligibility Determination; Health Services Accessibility /standards /economics; Humans; Insurance Coverage; Insurance, Pharmaceutical Services /economics /standards; Life Expectancy; Medical Assistance /organization & Models, Econometric; Organizational Innovation; Quality-Adjusted Life Years; Research Support, U.S. Gov't, P.H.S.; State Health Plans /organization & United States /epidemiology; administration; administration; numerical data AccessionNumber 22002008162 Date bibliographic record published 31/01/2005 Date abstract record published 31/01/2005 |
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