Isoniazid prophylactic therapy for tuberculosis in HIV-seropositive patients: a least-cost analysis
Masobe P, Lee T, Price M
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
Tuberculosis isoniazid chemoprophylactic (TIP) therapy in HIV-positive people.
Type of intervention
Treatment; primary prevention.
Economic study type
Cost-effectiveness analysis
Study population
HIV-infected adults.
Setting
Hospital setting. The economic study was carried out at the University of Witwatersrand, Johannesburg, South Africa.
Dates to which data relate
Effectiveness data were obtained from the period 1970 -1993. Resource data were obtained from a 1995 study. 1993 prices were used.
Source of effectiveness data
The estimate for final outcome was derived from a review of previously completed studies.
Modelling
A computer spreadsheet model was used to estimate costs and benefits.
Outcomes assessed in the review
The outcome assessed was the efficacy of preventive therapy with isoniazid in HIV-associated tuberculosis over an 8 year period.
Study designs and other criteria for inclusion in the review
No inclusion/exclusion criteria were stated.
Sources searched to identify primary studies
Not stated.
Criteria used to ensure the validity of primary studies
Not stated.
Methods used to judge relevance and validity, and for extracting data
Not stated.
Number of primary studies included
Two studies.
Methods of combining primary studies
Not stated.
Investigation of differences between primary studies
Not stated.
Results of the review
The overall incidence preventing capability of TIP therapy in HIV infected populations had been successful in 96.7% and 99% of those on isoniazid (compared to 92.9% in a placebo in the last case).
Measure of benefits used in the economic analysis
Number of tuberculosis cases prevented.
Direct costs
Quantities and costs were analysed separately. All costs were discounted at 4%, and quoted in 1993 prices, and included: diagnosis costs; hospitalisation and post-hospital care costs; ambulatory drugs' costs; SAC clinical service costs; transport costs; disease related to contact costs; costs of treating relapsed cases; and costs of managing side-effects.
Currency
South African rands (R).
Sensitivity analysis
One way sensitivity analysis varied the discount rate (1-8%); two way sensitivity analysis was applied to the compliance rate (41-68.5%) and annual risk of clinical TB (5-7.9%).
Estimated benefits used in the economic analysis
A chemoprophylaxis programme would have resulted in 21800 fewer active TB cases per 100,000 HIV positive persons over the 8 year period.
Cost results
The cost was 51,333,954R if tuberculosis isoniazid prophylaxis was undertaken, thus averted future costs are 40,551,952R.
Synthesis of costs and benefits
A synthesis of costs and benefits was not undertaken by the authors because the intervention was the dominant strategy.
Authors' conclusions
The economic appraisal suggested that prevention of tuberculosis by isoniazid chemoprophylaxis therapy was more cost-effective than treatment of incidences of the disease in patients with HIV/AIDS. This was dependant, however, on the rates of compliance, the annual risk of developing the disease and the validity of efficacy and protective assumptions of the treatment.
CRD Commentary
Detailed costing information was provided, but the review of the clinical studies was not undertaken systematically. The evidence regarding the duration of the protective benefits of isoniazid was poor, as the authors noted. Results were robust to sensitivity analysis. The generalisability of results is limited, because the authors only analysed a few primary sources of outcome data.
Implications of the study
A full cost effectiveness analysis is required, with a synthesis of costs and benefits and justification for study inclusions, in order that such conclusions be empirically supported.
Source of funding
None stated.
Bibliographic details
Masobe P, Lee T, Price M. Isoniazid prophylactic therapy for tuberculosis in HIV-seropositive patients: a least-cost analysis. South African Medical Journal 1995; 85(2): 75-81