|
Cost-effectiveness of an HIV prevention intervention for mentally ill adults |
Pinkerton S D, Johnson-Masotti A P, Otto-Salaj L L, Stevenson L Y, Hoffmann R G |
|
|
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 Small-group interventions for reducing the risk of human immunodeficiency virus (HIV) were studies. The interventions consisted of seven small-group sessions and two booster sessions. No further details were reported.
Study population The study population comprised mentally ill women. Male patients were excluded because the intervention had been found to be ineffective in reducing HIV in men.
Setting The setting was primary care. Five county-supported community mental health clinics in Milwaukee (WI) were used.
Dates to which data relate The effectiveness data were collected from studies published between 1996 and 1998. The cost data were collected from studies published between 1997 and 1998. The price year was 1999.
Source of effectiveness data The effectiveness data were derived from a review and synthesis of completed studies.
Modelling A mathematical model was used to combine information on transmission probabilities, and the number of protected and unprotected vaginal and anal sex acts. It was also used to estimate the probability of an uninfected woman becoming infected and to estimate the number of infections averted by the intervention.
Outcomes assessed in the review The following outcomes were assessed in the review:
the HIV transmission probability per act for receptive anal intercourse;
the HIV transmission probability per act for receptive vaginal intercourse;
the HIV transmission probability per act for insertive anal or vaginal intercourse;
HIV prevalence;
condom effectiveness; and
overlap among the participants' sexual partners.
Study designs and other criteria for inclusion in the review The authors selected references that provided information relevant to their mathematical model.
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 Seven studies were included in the review.
Methods of combining primary studies It was unclear how the results were combined to obtain the base-case parameter values. The studies were also used to define the limits for the sensitivity analysis.
Investigation of differences between primary studies Results of the review The base-case and sensitivity analysis ranges were as follows:
the HIV transmission probability per act for receptive anal intercourse was 0.02 (0.008 - 0.032);
the HIV transmission probability per act for receptive vaginal intercourse was 0.001 (0.0005 - 0.0015);
the HIV transmission probability per act for insertive anal or vaginal intercourse was 0.0006 (0.0003 - 0.0009);
condom effectiveness was 90% (80 - 100);
HIV prevalence was 2.4%;
overlap among the participants' sexual partners was 25% (0 - 50).
Methods used to derive estimates of effectiveness The authors made some assumptions to supplement their effectiveness estimates.
Estimates of effectiveness and key assumptions The authors assumed that the participants changed their behaviour following the intervention for only 6 months.
Measure of benefits used in the economic analysis The summary measure of benefit was the quality-adjusted life-years (QALYs). The estimate of QALYs saved by preventing someone becoming infected was taken from a published paper (see Other Publications of Related Interest) and was adjusted for age.
Direct costs The costs were estimated from a societal perspective with discounting at 3% for the base-case analysis (0 to 5% in the sensitivity analysis). The authors stated that the analysis incorporated all HIV-related costs and consequences regardless of who paid them. The categories considered were staff compensation, materials, transportation, facilities (rent, utilities, insurance) and food. The costs associated with staff training and developing the intervention materials were included, but survey work and activities associated with the scientific objective of the study were excluded. The authors reported that the actual costs of the intervention were measured retrospectively from existing records such as receipts, invoices and personnel records. The price year was 1999 and the prices were inflated using the Consumer Price Index.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs No indirect costs were included in the analysis.
Sensitivity analysis A sensitivity analysis was carried out to estimate the impact of uncertainty in the "retrospective cost ascertainment". The intervention cost was inflated or deflated by 25%.
Estimated benefits used in the economic analysis When a 40-year-old becomes infected, 9 years of life and 6 QALYs are lost Alternatively, for the full sample, the intervention averted 0.064 infections, thus saving 0.4 QALYs.
When restricted to sexually active women, the intervention averted 0.104 infections per 100 participants, thus saving 0.64 QALYs.
Cost results The total cost of the intervention was $29,201, and the cost per participant was $679.
The cost per 100 participants was $67,910.
The cost per 100 participants net of averted medical care costs was $54,080.
Synthesis of costs and benefits The cost per QALY saved for the full sample (after adjusting for avoided medical care costs) was $136,295.
The cost per QALY saved when restricted to sexually active women (after adjusting for avoided medical care costs) was $71,367.
The cost-utility ratio was moderately sensitive to condom effectiveness, partnership overlap and a 25% inflation or deflation in the intervention cost. It was also sensitive to the per-act transmission probability and the discount rate. Similar reactions were found with the sub-group of sexually active women.
Authors' conclusions The authors concluded that the estimated cost-utility ratios exceeded those for interventions generally considered cost-effective, but were less than the threshold considered not cost-effective. They therefore suggested that the intervention could be cost-effective for women with mental illness if implemented with sexually active women in areas with a high prevalence of human immunodeficiency virus (HIV).
CRD COMMENTARY - Selection of comparators The authors aimed to assess the cost-effectiveness of a small-group intervention for helping mentally ill adults to reduce their risk for HIV. The comparator was a health promotion intervention that included topics other than HIV. The rationale for this study was that, at the time of the analysis, there was no evidence relating to mentally ill individuals.
Validity of estimate of measure of effectiveness The authors did not state that a systematic review of the literature had been carried out. As a mathematical model was used, evidence from published sources was selected if it provided information relevant to the model. It was unclear how the authors selected parameters for the base-case. However, the range of published estimates formed the basis for the sensitivity analysis, which enabled the authors to explore the impact of differences between the primary studies.
Validity of estimate of measure of benefit The estimation of benefits was modelled with basic utility data taken from a published source relating to HIV patients.
Validity of estimate of costs A societal perspective was adopted for the analysis. The costs relevant to this perspective were discussed and estimated. The patients' opportunity costs of participating in the study were included in the analysis. The opportunity costs were estimated using the monetary incentives paid to intervention participants as a proxy. There was a substantial cost-difference between the targeted and non-targeted intervention. Therefore, small omissions in cost, from any source, are unlikely to affect the principal conclusion that the intervention is more cost-effective when targeted at sexually active women. The costs and the quantities were not reported separately.
Other issues The authors were unable to directly compare their results, as this was the first study examining cost-effectiveness in mentally ill populations. Nevertheless, the authors did compare the resultant cost-effectiveness ratios in order to make statements about the relative cost-effectiveness of the intervention. The issue of generalisability to other settings was addressed through the sensitivity analysis, which allowed the authors to conclude "a similar intervention would be cost-effective in regions with moderate to high HIV prevalence". The results were not presented selectively and the conclusions accurately reflected the results presented. The study focused on women in preference to men. This was well justified and, again, well reflected in the results and conclusions. Several limitations were discussed. For example, the retrospective nature of the costing and the use of self-reporting of sexual risk behaviours.
Implications of the study The authors made no recommendations for policy or practice as a result of their study, although the preference for targeting the intervention to sexually active women was clear. The authors called for further research to explore the difference in effectiveness between men and women, and to assess whether briefer, less intense sessions could achieve similar effects.
Source of funding Supported by the National Institute of Mental Health, grant numbers R01-MH55440, R01-MH49031 and P30-MH52776.
Bibliographic details Pinkerton S D, Johnson-Masotti A P, Otto-Salaj L L, Stevenson L Y, Hoffmann R G. Cost-effectiveness of an HIV prevention intervention for mentally ill adults. Mental Health Services Research 2001; 3(1): 45-55 Other publications of related interest Holtgrave DR, Pinkerton SD. The cost-effectiveness of small group and community-level interventions. In: Holtgrave DR, editor. Handbook of economic evaluation of HIV prevention programs. New York: Plenum Press; 1998. p. 119-26.
Indexing Status Subject indexing assigned by NLM MeSH Acquired Immunodeficiency Syndrome /complications /economics; Adult; Cost-Benefit Analysis; Female; HIV Seropositivity /complications /economics; Health Education /economics; Humans; Mental Disorders /complications /economics; Mental Health Services /economics; Quality-Adjusted Life Years; Safe Sex; Value of Life /economics; Wisconsin AccessionNumber 22002006101 Date bibliographic record published 30/09/2004 Date abstract record published 30/09/2004 |
|
|
|