Previous Article | Next Article 
Clinical and Vaccine Immunology, August 2009, p. 1170-1175, Vol. 16, No. 8
1071-412X/09/$08.00+0 doi:10.1128/CVI.00168-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Short-Term Reproducibility of a Commercial Interferon Gamma Release Assay
A. K. Detjen,1*
L. Loebenberg,2
H. M. S. Grewal,3
K. Stanley,2
A. Gutschmidt,2
C. Kruger,2
N. Du Plessis,2
M. Kidd,4
N. Beyers,1
G. Walzl,2 and
A. C. Hesseling1
Desmond Tutu Tuberculosis Centre, Department of Paediatrics and Child Health, Faculty of Health Sciences, Stellenbosch University, Tygerbery, South Africa,1 DST/NRF Centre of Excellence in Biomedical Tuberculosis Research and MRC Centre for Molecular and Cellular Biology, Department of Biomedical Sciences, Stellenbosch University, Tygerberg, South Africa,2 The Gade Institute, Section for Microbiology and Immunology, University of Bergen and Haukeland Hospital, Bergen, Norway,3 Centre for Statistical Consultation, Department of Statistics and Actuarial Sciences, Stellenbosch University, Tygerbery, South Africa4
Received 10 April 2009/ Returned for modification 12 May 2009/ Accepted 8 June 2009
Interferon gamma release assays (IGRAs) have been shown to be sensitive and highly specific for the detection of immune memory against Mycobacterium tuberculosis. Little is known about the reproducibility and within-person variability of these assays. Various aspects of short-term reproducibility of a commercial IGRA, the QuantiFERON-TB Gold In-Tube (QFT-IT) assay, were assessed. The QFT-IT assay was performed twice within 3 days in 27 health care workers in Cape Town, South Africa. Two sets of tests were performed by different operators on day 1, and one set was performed on day 3. Aspects such as interoperator, intraoperator, day-to-day variability, and test-retest variability as well as different the storage methods of plasma were investigated. Seventeen of 27 (63%) of participants had at least one positive QFT-IT text; six had discordant results. The agreement of all aspects studied was high, with kappa values between 0.82 and 1.00 for dichotomous measures, and interclass correlations (ICC) of 0.809 to 0.965 were observed for continuous gamma interferon (IFN-
) measures. The variability of the magnitude of response was highest comparing measures obtained from individuals on different days (ICC of 0.809). The magnitude of the IFN- responses between assays performed for individual participants was variable, with ranges from 0.03 to 11 IU/ml, resulting is discordant results for five participants. The results indicate that the QFT-IT assay is a robust and highly reproducible assay. Considerable intraindividual variability occurs in the magnitude of IFN- responses, which may influence the interpretation of serial measures.
* Corresponding author. Mailing address: Desmond Tutu Tuberculosis Centre, Department of Paediatrics and Child Health, Stellenbosch University, P.O. Box 19063, Tygerberg 7505, South Africa. Phone: 27 21 938 9177. Fax: 27 21 938 9719. E-mail: anne.detjen{at}charite.de
Published ahead of print on 17 June 2009.
Clinical and Vaccine Immunology, August 2009, p. 1170-1175, Vol. 16, No. 8
1071-412X/09/$08.00+0 doi:10.1128/CVI.00168-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Copyright © 2010 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»