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Preventing HIV/AIDS among high-risk urban women: the cost-effectiveness of a behavioral group intervention |
Holtgrave D R, Kelly J 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 Cognitive-behavioural group intervention for HIV prevention in high-risk urban women.
Study population Urban women at high risk of HIV infection.
Setting Primary care. The economic study was carried out in Milwaukee, Wisconsin, USA.
Dates to which data relate The data for the effectiveness analysis were collected mainly from a study carried out in the authors' own institution in 1992 and published in 1994. The number of quality-adjusted life-years (QALY) saved per HIV infection averted was obtained from a study published in 1995. Single sex act transmission probability andsingle sex partner transmission probability were extracted from studies published between 1990 and 1994. The data for the resource use were mainly obtained from the study carried out in the authors' own institution. The prices used were those of 1992.
Source of effectiveness data Effectiveness data were derived from a single study, a review of published studies, and authors' assumptions.
Link between effectiveness and cost data The costing was undertaken retrospectively on the same patient sample as that used in the effectiveness analysis.
Study sample No power calculations were reported. A total of 197 women was included in the study. One hundred (100) patients were included in the intervention group, and 97 were allocated to the control group, receiving nutritional information and skills unrelated to HIV. A total of 87% of subjects were African-American and more than 97% were unemployed, with an average age of 29 years and an average educational level of 11 years.
Study design The study was a randomized controlled trial. The duration of follow-up was three months. No loss to follow up was reported.
Analysis of effectiveness The principle (intention to treat or treatment completers only) used in the analysis was not stated. The primary health outcome used was behavioural change, based on the comparison between control and intervention with respect to condom use (in terms of proportion of all cases and proportion of all male sex partners).
Effectiveness results At three months, the intervention group used condoms on 56% of the occasions involving vaginal intercourse against 32% of the time for the control group. At the same time point, the condom was used with 66% of the male sex partners in the intervention group against 48% for the control.
Clinical conclusions The study revealed that "HIV-related risk behaviour can be modified successfully with behavioural interventions".
Modelling A standard cumulative probability equation was used to convert behavioural effects into estimates of the number of HIV infections averted. The model was based on the idea that each sex act carries some risk of infection ("per act" model), as opposed to the per partner model (each new partner represents a risk of HIV infection), to which the former could be converted by adjusting the value of some parameters.
Outcomes assessed in the review The main outcomes derived from the literature were the number of quality-adjusted life-years (QALY) saved per HIV infection averted (adjusted for the difference in age), single sex act transmission probability, andsingle sex partner transmission probability.
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 Four studies were included.
Methods of combining primary studies Investigation of differences between primary studies Results of the review The number of quality-adjusted life-years (QALY) saved per HIV infection averted (adjusted for the difference in age) was 7.64 (5-10). Single sex act transmission probability was 0.0155and single sex partner transmission probability was 0.25.
Methods used to derive estimates of effectiveness Estimates of effectiveness were also based on authors' assumptions.
Estimates of effectiveness and key assumptions The authors assumed that all subjects in the study cohort were HIV seronegative at the start of the intervention. Furthermore, it was assumed that all HIV transmission risk stemmed from male sex partners.
Measure of benefits used in the economic analysis The outcome measure used was HIV infections averted and QALYs saved. A model was used to convert behavioural effects (condom use) into estimates of the number of HIV infections averted. The valuation method for health states and related details were not reported.
Direct costs Costs were discounted. Quantities were not reported separately. The unit costs were reported separately. The costs measured were operating and overhead costs. The boundary adopted was society. The estimate of costs for the intervention was based on actual data and on an estimate published in 1994. The sources of quantities reported were information held by the principal investigator in the clinical study, and the records from the authors' own institution. The prices used were those of 1992.
Indirect Costs Costs were discounted. The quantities of resources used were not reported. The costs measured were the market value of participants' time. The estimation of costs was based on actual data from 1992. The prices used were those of 1992.
Sensitivity analysis The parameters varied in the sensitivity analysis were 'sex partners' HIV seroprevalence', 'condom use with intervention, per act', condom use with intervention, per partner', 'number of partners per client', 'incentives per client per session', 'indirect (overhead) cost rate', number of QALYs saved per prevention and discounted medical treatment costs. One-way and two-way sensitivity analyses were carried out.
Estimated benefits used in the economic analysis The number of HIV cases averted was 0.38. The number of QALYs gained with intervention relative to the comparator was estimated to be 2.90, using a 5% discount rate.
Cost results The estimated total cost of the intervention was $26,914. The total saved cost was $21,80. Therefore, the net cost of the intervention group (100 patients) turned out to be $5,634, in 1992 prices discounted at 5%.
Synthesis of costs and benefits The cost per QALY gained was used as a synthesismeasure. The cost per QALY gained for the intervention, relative to the 'do-nothing' alternative, was $2,024. The sensitive parameters found in the analysis were the 'per-act transmission probability' and 'local HIV seroprevalence'. These parameters yielded a high cost-utility ratio ($234,020) with the 'per-act model transmission probability' reaching 0.0014 (baseline 0.0155) and 'local HIV seroprevalence' being 0.01 (baseline 0.03), jointly.
Authors' conclusions Th authors argued that "It is justifiable to conclude that the intervention is cost-effective under most scenarios considered and is cost saving under some".
CRD COMMENTARY - Selection of comparators The reason for the choice of the comparator is clear. Validity of estimate of measure of benefit In principle, the estimate of measure of benefit used in the economic analysis is likely to be internally valid given the design used (a randomized controlled trial), however the estimation of infections averted was modelled rather than directly measured. The authors also note that the estimation of benefits is likely to be conservative due to the short observation period (less than 1 year). Validity of estimate of costs The resource quantities were not reported separately from the prices, however adequate details of methods of cost estimation were given. Other issues The authors' conclusions were justified on the grounds of the sensitivity analysis. The authors made clear that generalisation of the results should be made only to organisations already delivering some type of "behaviourally based" HIV prevention programme (no capital or start-up costs were included). Source of funding Supported in part by grants RO1-MH55440 and P30-MH52776 from the National Institute of Mental Health.
Bibliographic details Holtgrave D R, Kelly J A. Preventing HIV/AIDS among high-risk urban women: the cost-effectiveness of a behavioral group intervention. American Journal of Public Health 1996; 86(10): 1442-1445 Indexing Status Subject indexing assigned by NLM MeSH Acquired Immunodeficiency Syndrome /economics /prevention & Adult; Condoms /utilization; Cost-Benefit Analysis; Female; Humans; Outcome and Process Assessment (Health Care); Preventive Health Services /economics; Quality-Adjusted Life Years; Retrospective Studies; Risk Factors; Sexual Behavior; Urban Population; control AccessionNumber 21996008287 Date bibliographic record published 31/07/1999 Date abstract record published 31/07/1999 |
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