Veille documentaire MTPH

Médecine du travail du personnel hospitalier

Within-subject variability of Mycobacterium tuberculosis-specific gamma interferon responses in German health care workers

Auteur     Felix C Ringshausen
Auteur     Albert Nienhaus
Auteur     José Torres Costa
Auteur     Heiko Knoop
Auteur     Stephan Schlösser
Auteur     Gerhard Schultze-Werninghaus
Auteur     Gernot Rohde
Résumé     Gamma interferon (IFN-γ) release assays (IGRAs) are used increasingly for the periodic tuberculosis (TB) screening of health care workers (HCWs), although data regarding the reproducibility and interpretation of serial testing results in countries with a low incidence of TB are scarce. The present study evaluated and compared the within-subject variability of dichotomous and continuous results of two commercial IGRAs, the QuantiFERON-TB Gold In-Tube (QFT) and the T-SPOT.TB (T-SPOT), in German HCWs during a 4-week period. Thirty-five immunocompetent HCWs with low or medium TB screening risk and without known recent TB exposure or tuberculin skin test application were tested repeatedly with both IGRAs at weekly intervals. A total of 158 valid results were obtained for each IGRA. Changes of about ±70% (QFT) and ±60% (T-SPOT) from the mean IFN-γ response accounted for 95% of the within-subject variability. However, according to the manufacturers’ cutoffs, inconsistent results were observed more frequently for the QFT (28.6%; four conversions, six reversions) than for the T-SPOT (8.6%; three reversions; P < 0.001). The overall agreement between the IGRAs was good. Regression toward the means accounted for a significant decline in mean IFN-γ responses of about 25% between successive visits for both IGRAs. Although both assays were highly reliable and reproducible, we observed substantial within-subject variability and regression toward the means during a 4-week period, which should be considered when interpreting serial testing results in comparable populations and settings. Our data support the use of borderline zones for the interpretation of serial IGRA results and the retesting of borderline positive results before offering preventive chemotherapy.
Publication     Clinical and Vaccine Immunology: CVI
Volume     18
Numéro     7
Pages     1176-1182
Date     Jul 2011

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