|
Tuberculosis screening of immigrants to low-prevalence countries: a cost-effectiveness analysis |
Schwartzman K, Menzies D |
|
|
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 screening of immigrants to low-prevalence countries.
Type of intervention Screening and primary prevention.
Economic study type Cost-effectiveness analysis.
Study population A hypothetical population of 20-year-old immigrants.
Setting Hospital. The economic study was carried out in Canada.
Dates to which data relate Effectiveness data were collected from studies published between 1963 and 1999. Resource use and cost data were collected from studies published between 1990 and 1999. The price year was 1997.
Source of effectiveness data Effectiveness data were derived from a literature review.
Modelling A 20-year time frame Markov model was used to determine the cost-effectiveness of the screening strategies.
Outcomes assessed in the review The review assessed the following outcomes: history of HIV infection, prevalence of active TB, TB-associated mortality, reactivation of TB-infection, secondary transmission of TB, specificity of diagnostic tests, medication use and side effects.
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 Summary statistics from individual studies.
Number of primary studies included At least 22 studies were included.
Methods of combining primary studies Investigation of differences between primary studies Results of the review Survival of later stage HIV-infected persons was 7 years compared to 90% survival for the first 6 years and 55% survival for the following 6 years for early stage HIV-infected persons. 25% of HIV-infected persons had advanced disease at screening. The prevalence of active TB was 2.3% among HIV-seronegative immigrants with TB infection. The prevalence of active TB among persons with TB infection was 4.6% with concomitant early-stage HIV disease and 9.2% with advanced HIV disease. The annual reactivation risk was 0.1% for HIV-negative individuals with TB infection but normal X-rays and 0.66% with abnormal X-rays. The incidence of active TB was 2.6% for early-stage HIV patients and 6.5% for later-stage HIV patients. Completion of 6 months of INH produced a 65% reduction in the annual risk of reactivation. Passively and actively diagnosed TB cases produced 3.5 and 1.5 infected contacts per case, respectively. Passively detected cases each generated 0.7 secondary active cases, whereas actively detected cases each generated 0.3 secondary active cases. Chest X-ray led to further investigation in 95% of active TB cases. 11% of infected individuals had abnormal X-rays. The specificity of X-ray TB testing, sputum microbiology, and tuberculin testing was 97.5%, 99%, and 87.5-97.5%, respectively. INH prophylaxis was prescribed in 73% of suitable candidates.
Measure of benefits used in the economic analysis The number of TB cases prevented was used as the measure of benefits. Benefits were discounted at an annual rate of 3%.
Direct costs Direct costs were discounted at an annual rate of 3%. Quantities and costs were reported separately. Direct costs included physician and personnel costs, equipment and supplies, medications, hospital bed costs, and overheads. The quantity/cost boundary adopted was that of the health service. The estimation of quantities and costs was based on actual data. Costs were obtained from the Montreal Chest Institute and Royal Victoria Hospital, and physician fees from the Quebec Health Insurance Board. The price year was 1997.
Currency Canadian dollars (Can$) (Can$1 = US$0.65).
Sensitivity analysis One-way sensitivity analyses were performed on all probabilities and costs. The conclusions of the base case analysis were robust across the various one-way sensitivity analyses conducted.
Estimated benefits used in the economic analysis For population 1, the number of active TB cases per 1,000 was 37.4 without screening, 35.8 with X-ray screening, and 32.8 with tuberculin skin screening.
For population 2, the number of active TB cases per 1,000 was 24.6 without screening, 23.4 with X-ray screening, and 21.7 with tuberculin skin screening.
For population 3, the number of active TB cases per 1,000 was 2.5 without screening, 2.3 with X-ray screening, and 2.2 with tuberculin skin screening.
Cost results For population 1, total costs per 1,000 amounted to Can$332,020 without screening, Can$338,310 with X-ray screening, and Can$436,390 with tuberculin skin screening.
For population 2, total costs per 1,000 were Can$218,250 without screening, Can$231,430 with X-ray screening, and Can$342,730 with tuberculin skin screening.
For population 3, total costs per 1,000 were Can$21,820 without screening, Can$51,170 with X-ray screening, and Can$62,640 with tuberculin skin screening.
Synthesis of costs and benefits For population 1, the incremental cost per case prevented was Can$3,943 with X-ray screening relative to no screening, and Can$32,601 with tuberculin skin screening relative to X-ray screening.
For population 2, the incremental cost per case prevented was Can$10,627 with X-ray screening relative to no screening, and Can$66,759 with tuberculin skin screening relative to X-ray screening.
For population 3, the incremental cost per case prevented was Can$236,496 with X-ray screening relative to no screening, and Can$68,799 with tuberculin skin screening relative to X-ray screening.
Authors' conclusions Compared with tuberculin skin testing, chest radiographic screening for TB among immigrants is more cost-effective. For immigrants from low-prevalence countries, both interventions are extremely costly with negligible impact. The cost-effectiveness of either strategy would be greatly enhanced by increased adherence to chemoprophylaxis recommendations. Radiographic screening of groups with a high prevalence of TB infection will then be likely save money.
CRD COMMENTARY - Selection of comparators A justification was given for the comparator used, namely no screening. You, as a user of the database, should decide if these health technologies are relevant to your own setting.
Validity of estimate of measure of benefit The authors did not state whether a systematic review of the literature had been undertaken and more details of the literature review could have been provided. Probabilities for the model were derived from primary studies. The estimation of benefits was obtained directly from the effectiveness analysis.
Validity of estimate of costs All categories of costs relevant to the perspective adopted were included in the analysis and costs and quantities were reported separately. Sensitivity analyses were performed on costs, but not on quantities. Fees were used to proxy prices. The price year was reported.
Other issues The authors did make appropriate comparisons of their findings with those from other studies and the issue of generalisability to other settings was addressed. The authors did not present their results selectively. The study examined 20-year-old immigrants to low-prevalence countries and this was reflected in the authors' conclusions. The analysis involved several uncertainties about the natural history of TB and HIV disease, diagnostic test performance, treatment outcomes, and costs. The cost estimates used were generally lower than costs at similar US centres.
Source of funding Dr Schwartzman was supported by the Fonds de la Recherche en Sante du Quebec Chercheur-Boursier Clinicien Award. Dr Menzies was supported by a Medical Research Council of Canada Scientist Award.
Bibliographic details Schwartzman K, Menzies D. Tuberculosis screening of immigrants to low-prevalence countries: a cost-effectiveness analysis. American Journal of Respiratory and Critical Care Medicine 2000; 161(3): 780-789 Indexing Status Subject indexing assigned by NLM MeSH AIDS-Related Opportunistic Infections /economics /epidemiology /prevention & Adult; Canada; Cost-Benefit Analysis; Cross-Sectional Studies; Emigration and Immigration /statistics & Female; Humans; Male; Mass Chest X-Ray /economics; Mass Screening /economics; Tuberculin Test /economics; Tuberculosis, Pulmonary /economics /epidemiology /prevention & control; control; numerical data AccessionNumber 22000000690 Date bibliographic record published 31/12/2000 Date abstract record published 31/12/2000 |
|
|
|