Comparison of interferon-gamma release assay versus tuberculin skin test for tuberculosis screening in inflammatory bowel disease.
OBJECTIVE
Reactivation of latent tuberculosis (TB) in inflammatory bowel disease (IBD) patients treated with antitumor necrosis factor-alpha medication is a serious problem. Currently, TB screening includes chest x-rays and a tuberculin skin test (TST). The interferon-gamma release assay (IGRA) QuantiFERON-TB Gold In-Tube (QFT-G-IT) shows better specificity for diagnosing TB than the skin test. This study evaluates the two test methods among IBD patients.


METHODS
Both TST and IGRA were performed on 212 subjects (114 Crohn's disease, 44 ulcerative colitis, 10 indeterminate colitis, 44 controls).


RESULTS
Eighty-one percent of IBD patients were under immunosuppressive therapy; 71% of all subjects were vaccinated with Bacille Calmette Guérin; 18% of IBD patients and 43% of controls tested positive with the skin test (P < 0.0001). Vaccinated controls tested positive more often with the skin test (52%) than did vaccinated IBD patients (23%) (P = 0.011). Significantly fewer immunosuppressed patients tested positive with the skin test than did patients not receiving therapy (P = 0.007); 8% of patients tested positive with the QFT-G-IT test (14/168) compared to 9% (4/44) of controls. Test agreement was significantly higher in the controls (P = 0.044) compared to the IBD group.


CONCLUSIONS
Agreement between the two test methods is poor in IBD patients. In contrast to the QFT-G-IT test, the TST is negatively influenced by immunosuppressive medication and vaccination status, and should thus be replaced by the IGRA for TB screening in immunosuppressed patients having IBD.
Schoepfer
Alain M
AM
Department of Gastroenterology, Inselspital, University of Bern, Switzerland.
Flogerzi
Beatrice
B
Fallegger
Silvia
S
Schaffer
Thomas
T
Mueller
Stefan
S
Nicod
Laurent
L
Seibold
Frank
F
D000998:Antiviral Agents; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000150:complications*; D007371:Interferon-gamma; D008403:Mass Screening; D011933:Reagent Kits, Diagnostic; D014374:Tuberculin Test; D014376:Tuberculosis / Q000150:complications / Q000175:diagnosis*
D000998:Antiviral Agents; D011933:Reagent Kits, Diagnostic; D007371:Interferon-gamma