This Article Full Text Full Text (PDF) Other Versions of this Article: CVI.00398-07v1 15/3/425    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Google Scholar Articles by Perry, S. Articles by Parsonnet, J. PubMed PubMed Citation Articles by Perry, S. Articles by Parsonnet, J.

Reproducibility of QuantiFERON-TB Gold In-Tube Assay

Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, California,¹ Santa Clara Valley Health and Hospitals System, San Jose, California²

Received 3 September 2007/ Returned for modification 7 November 2007/ Accepted 6 January 2008

Studies are needed to characterize the reproducibility of QuantiFERON-TB Gold (QFT-G) for targeted U.S. screening populations. Members of northern California households were tested with the QFT-G in-tube assay (QFT-G-IT) at two home visits 3 months apart. Reproducibility and agreement with the tuberculin skin test (TST) were assessed. Monte Carlo simulation was used to evaluate the role of test-related error. Of 63 individuals (49 adults and 14 children) completing QFT-G-IT at both time points, 79% were foreign-born (98% from Latin America) and 68% reported Mycobacterium bovis BCG vaccination. At the baseline visit, 23 (37%) were TST positive and 15 (24%) were QFT-G-IT positive ( = 0.48 [± 0.11]). At 3 months, 3/48 (6.3%; 95% confidence interval [95CI], 2 to 17) of those initially QFT-G-IT negative converted, and 5/15 (33%; 95CI, 15 to 58) of those initially QFT-G-IT positive reverted. Among the 8 individuals with inconsistent QFT-G-IT results, the maximum gamma interferon response at either visit was 0.68 IU/ml versus means of 4.99 (± 3.74) and 6.95 (± 5.6) for 10 persistent positives at the first and second visits, respectively. Expected false-reversion and -conversion rates were 32% (90CI, 25 to 39%) and 6.95% (90CI, 4.6 to 9.8%) when the sensitivity and specificity were assumed to average 70% and 98%, respectively. Transient responses to QFT-G-IT are common, and low positive results need to be interpreted with caution. Further studies are needed to characterize the predictive value of the test for U.S. foreign-born and other targeted screening populations.

Published ahead of print on 16 January 2008.