Specific Interferon γ Detection for the Diagnosis of Previous Q Fever

• Published in: Clinical infectious diseases Vol. 56; no. 12; pp. 1742 - 1751
• Main Authors: Schoffelen, Teske, Joosten, Leo A. B., Herremans, Tineke, de Haan, Anton F. J., Ammerdorffer, Anne, Rümke, Hans C., Wijkmans, Clementine J., Roest, Hendrik I. Jan, Netea, Mihai G., van der Meer, Jos W. M., Sprong, Tom, van Deuren, Marcel
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 15.06.2013
• Subjects: Abbreviations; Aged; Antigens; ARTICLES AND COMMENTARIES; Bacterial diseases; Bacteriological Techniques - methods; Biological and medical sciences; Coxiella burnetii; Coxiella burnetii - immunology; Female; Human bacterial diseases; Humans; Infections; Infectious diseases; Interferon-gamma - analysis; Interferon-gamma - immunology; Interferon-gamma Release Tests - methods; Interferons; Male; Medical sciences; Middle Aged; Q fever; Q Fever - diagnosis; Q Fever - immunology; Reproducibility of Results; Rickettsial diseases; ROC Curve; Serologic Tests - methods; Serology; Skin tests; Skin Tests - methods; Statistics, Nonparametric; Tropical bacterial diseases; Trucks; Vaccination; Infection; Rickettsialosis; Rickettsial infection; Q fever; Bacteriosis; Diagnosis; Gamma interferon; Coxiella burnetii; skin test; interferon γ; serology
• ISSN: 1058-4838; 1537-6591
• DOI: 10.1093/cid/cit129

Background. Current practice for diagnosis of Q fever, caused by the intracellular pathogen Coxiella burnetii, relies mainly on serology and, in prevaccination assessment, on skin tests (STs), which both have drawbacks. In this study, C. burnetii—specific interferon γ (IFN-γ) production was used as a new diagnostic tool for previous Q fever, circumventing most of these drawbacks. Our aim was to compare this test to serology and ST. Methods. One thousand five hundred twenty-five individuals from an endemic area with a risk for chronic Q fever were enrolled. IFN-γ production was measured after in vitro stimulation of whole blood with C. burnetii antigens. Various formats using different C. burnetii antigens were tested. Serology and ST were performed in all individuals. Results. In all assay formats, C. burnetii—specific IFN-γ production was higher (P < .0001) in seropositive or ST-positive subjects than in seronegative and ST-negative subjects. Whole blood incubated for 24 hours with C. burnetii Nine Mile showed optimal performance. After excluding subjects with equivocal serology and/or borderline ST results, IFN-γ production was 449 ± 82 pg/mL in the positive individuals (n = 219) but only 21 ± 3 pg/mL in negative subjects (n = 908). Using Bayesian analysis, sensitivity and specificity (87.0% and 90.2%, respectively) were similar to the combination of serology and ST (83.0% and 95.6%, respectively). Agreement with the combination of serology and ST was moderate (84% concordance; κ = 0.542). Conclusions. Specific IFN-γ detection is a novel diagnostic assay for previous C. burnetii infection and shows similar performance and practical advantages over serology and ST. Future studies to investigate the clinical value in practice are warranted.