Cost-effectiveness of interferon-gamma release assay screening for latent tuberculosis infection treatment in Germany.
OBJECTIVE
To assess the cost-effectiveness of the new QuantiFERON-TB Gold In-Tube (QFT-G) [Cellestis; Carnegie, VIC, Australia] assay for screening and treating of persons who have had close contact with tuberculosis (TB) patients and are suspected of having latent tuberculosis infection (LTBI) [hereafter called close-contacts] in Germany.


METHODS
The health and economic outcomes of isoniazid treatment of 20-year-old close-contacts were compared in a Markov model over a period of 20 years, using two different cutoff values for the tuberculin skin test (TST), the QFT-G assay alone, or the QFT-G assay as a confirmatory test for the TST results.


RESULTS
QFT-G assay-based treatment led to cost savings of $542.9 and 3.8 life-days gained per LTBI case. TST-based treatment at a 10-mm induration size cutoff gained $177.4 and 2.0 life-days gained per test-positive contact. When the cutoff induration size for the TST was reduced to 5 mm, the incremental cost-effectiveness ratio fell below the willingness-to-pay threshold ($30,170 per life-years gained) but resulted in unnecessary treatment of 77% of contacts owing to false-positive TST results. Combination with the 5-mm induration size TST cutoff value compared to the results of the QFT-G assay alone reduced the total costs per 1,000 contacts by 1.8% to $222,869. The number treated to prevent 1 TB case was 22 for the two QFT-G assay-based procedures, 40 for the TST at a cutoff induration size of 10 mm, and 96 for the TST at a cutoff induration size of 5 mm. When the sensitivity rates of the TST and the QFT-G assay were compounded, the QFT-G assay strategy alone was slightly less costly (0.6%) than the two-step approach.


CONCLUSIONS
Using the QFT-G assay, but especially combining the QFT-G assay following the TST screening of close-contacts at a cutoff induration size of 5 mm before LTBI treatment is highly cost-effective in reducing the disease burden of TB.
Diel
Roland
R
School of Public Health, c/o Institute for Medical Sociology, Heinrich Heine University, Post Box 101007, D-40001 Düsseldorf, Germany. Roland.Diel@uni-duesseldorf.de
Nienhaus
Albert
A
Loddenkemper
Robert
R
D000328:Adult; D000995:Antitubercular Agents / Q000627:therapeutic use; D002353:Carrier State / Q000175:diagnosis; D003362:Cost-Benefit Analysis / Q000706:statistics & numerical data; D005189:False Positive Reactions; D005260:Female; D005858:Germany; D006801:Humans; D007371:Interferon-gamma / Q000097:blood*; D007538:Isoniazid / Q000627:therapeutic use; D008297:Male; D008390:Markov Chains; D008403:Mass Screening / Q000191:economics* / Q000379:methods; D008962:Models, Theoretical; D012680:Sensitivity and Specificity; D014374:Tuberculin Test / Q000191:economics* / Q000379:methods; D014376:Tuberculosis / Q000175:diagnosis* / Q000188:drug therapy*
D000995:Antitubercular Agents; D007371:Interferon-gamma; D007538:Isoniazid