title: Evaluation of an IFN-gamma assay in the diagnosis of latent tuberculosis in patients with psoriasis in a highly endemic setting.
abstract: Screening for latent tuberculosis infection is mandatory before starting anti-tumour necrosis factor treatments, but its diagnosis still poses a challenge. While studies performed in developed countries have demonstrated superior performance of T-cell based interferon-γ release assay (IGRA) compared with the tuberculin skin test, there is a debate about whether this holds true in tuberculosis endemic areas. The performance of an IGRA kit T-SPOT.TB was evaluated in 33 moderate-to-severe untreated psoriasis patients and, as controls, 30 patients with common dermatological diseases at a tuberculosis highly endemic setting. The frequency of positive tuberculin skin test responses and induration size in controls were higher than in psoriasis patients (53% vs. 18% and 9.3 ± 1.4 vs. 2.6 ± 0.7 mm, respectively, p < 0.001). In contrast, the frequency of positive response and mean number of spots elicited with the T-SPOT.TB test were not significantly different between patients and controls (47% vs. 43% and 14.7 ± 3.2 vs. 20.5 ± 3.1 spots/well, respectively). The two tests presented good agreement in the control, but not the psoriasis group (κ values of 0.625 and 0.375, respectively). Thus, in a highly tuberculosis-endemic setting the T-SPOT.TB test was superior to the tuberculin skin test in diagnosing latent tuberculosis infection in psoriasis, probably because the immune dysregulation of psoriasis shows a lower interference in the in vitro test.
authors.affiliation: Psoriasis Out-patient Service, Clinics Hospital, Federal University of State of Pernambuco, Brazil. emersonderma@terra.com.br
authors.forename: Emerson
authors.initials: E
authors.lastname: de Andrade Lima
authors.forename: Mariana
authors.initials: M
authors.lastname: de Andrade Lima
authors.forename: Virgínia M Barros
authors.initials: VM
authors.lastname: de Lorena
authors.forename: Yara
authors.initials: Y
authors.lastname: de Miranda Gomes
authors.forename: Omar
authors.initials: O
authors.lastname: Lupi
authors.forename: Gil
authors.initials: G
authors.lastname: Benard
mesh_terms: D000328:Adult; D000942:Antigens, Bacterial / Q000276:immunology; D001426:Bacterial Proteins / Q000276:immunology; D001938:Brazil; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000097:blood; D059425:Interferon-gamma Release Tests; D055985:Latent Tuberculosis / Q000150:complications / Q000175:diagnosis* / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D011565:Psoriasis / Q000150:complications*; D014374:Tuberculin Test; D055815:Young Adult
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis; D007371:Interferon-gamma