Comparison of an in vitro tuberculosis interferon-gamma assay with delayed-type hypersensitivity testing for detection of latent Mycobacterium tuberculosis: a pilot study in rheumatoid arthritis.
OBJECTIVE
Recommendations for screening for latent Mycobacterium tuberculosis (MTB) infection have been proposed but are not well studied in patients with rheumatoid arthritis (RA). We estimated the prevalence of anergy in RA and evaluated different methods to detect MTB exposure.


METHODS
This was a prospective pilot study of 61 patients with RA and 42 healthy controls. Tuberculin skin test (TST) antigen, Candida, and tetanus toxoid were injected intradermally using the Mantoux method. Subjects negative for TST returned for a second-step test. Whole-blood interferon-gamma (IFN-gamma) release to mycobacterial antigens was evaluated with the first-generation QuantiFeron test (QIFN).


RESULTS
Cutaneous anergy in patients with RA was not significantly different than healthy controls (p = 0.154), and was not affected by disease modifying antirheumatic drugs (p = 0.270). In patients with RA, 16.4% had positive TST with 10 mm cutoff vs 11.9% of controls. Using a 5 mm cutoff, 21.3% of patients with RA were positive, and this increased to 29.5% with a second-step TST. QIFN detected MTB exposure in 18% of patients with RA and 19% of controls (p = 0.897). However, indeterminate QIFN tests were higher in RA patients (11.5%) compared to controls (2.4%), demonstrating a lower sensitivity to detect latent MTB.


CONCLUSIONS
Cutaneous anergy may be less common than previously reported in patients with RA. patients. However, the single-step TST and 10 mm cutoff may fail to detect all cases of latent exposure in RA patients. High rates of indeterminate results in QIFN testing suggest that QIFN should not be employed as an alternative, single-screening test in patients with RA. These pilot results require confirmation in larger studies to determine the optimal screening strategy in RA.
Greenberg
Jeffrey D
JD
Department of Rheumatology, NYU-Hospital for Joint Diseases, New York, New York, USA.
Reddy
Soumya M
SM
Schloss
Shari G
SG
Kurucz
Oliver S
OS
Bartlett
Susan J
SJ
Abramson
Steven B
SB
Bingham
Clifton O
CO
D000328:Adult; D000942:Antigens, Bacterial / Q000494:pharmacology*; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000150:complications* / Q000188:drug therapy; D005260:Female; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000276:immunology*; D007371:Interferon-gamma / Q000097:blood*; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D010865:Pilot Projects; D015995:Prevalence; D011446:Prospective Studies; D014374:Tuberculin Test / Q000379:methods*; D014376:Tuberculosis / Q000175:diagnosis* / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors
D000942:Antigens, Bacterial; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma