Interferon-gamma release assays and TB screening in high-income countries: a cost-effectiveness analysis.
OBJECTIVE
Interferon-gamma release assays (IGRA) are now available alternatives to tuberculin skin testing (TST) for detection of latent tuberculosis infection (LTBI). We compared the cost-effectiveness of TST and IGRA in different populations and clinical situations, and with variation of a number of parameters.


METHODS
Markov modelling was used to compare expected TB cases and costs over 20 years following screening for TB with different strategies among hypothetical cohorts of foreign-born entrants to Canada, or contacts of TB cases. The less expensive commercial IGRA, Quanti-FERON-TB Gold (QFT), was examined. Model inputs were derived from published literature.


RESULTS
For entering immigrants, screening with chest radiograph (CXR) would be the most and QFT the least cost-effective. Sequential screening with TST then QFT was more cost-effective than QFT alone in all scenarios, and more cost-effective than TST alone in selected subgroups. Among close and casual contacts, screening with TST or QFT would be cost saving; savings with TST would be greater than with QFT, except in contacts who were bacille Calmette-Guérin (BCG) vaccinated after infancy.


CONCLUSIONS
Screening for LTBI, with TST or QFT, is cost-effective only if the risk of disease is high. The most cost-effective use of QFT is to test TST-positive persons.
Oxlade
O
O
Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University, Montreal, Canada.
Schwartzman
K
K
Menzies
D
D
D015415:Biomarkers / Q000097:blood; D002170:Canada / Q000453:epidemiology; D003362:Cost-Benefit Analysis; D019049:Developed Countries; D004641:Emigration and Immigration; D006801:Humans; D015994:Incidence; D007182:Income; D007371:Interferon-gamma / Q000097:blood*; D008390:Markov Chains; D008403:Mass Screening / Q000191:economics* / Q000379:methods*; D013902:Radiography, Thoracic / Q000191:economics; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000097:blood / Q000175:diagnosis* / Q000191:economics / Q000453:epidemiology
D015415:Biomarkers; D007371:Interferon-gamma