Tuberculosis screening in patients with psoriasis before antitumour necrosis factor therapy: comparison of an interferon-gamma release assay vs. tuberculin skin test.
BACKGROUND
Antitumour necrosis factor (anti-TNF) treatments may reactivate latent tuberculosis infection (LTBI). For detecting LTBI, the tuberculin skin test (TST) has low sensitivity and specificity. Interferon-gamma release assays (IGRA) have been shown to be more sensitive and specific than TST.


OBJECTIVE
To compare the TST and the T-SPOT.TB IGRA for identifying LTBI in patients with psoriasis before anti-TNF treatment.


METHODS
A retrospective study was carried out over a 4-year period on patients with psoriasis requiring anti-TNF treatment. All were subjected to the TST, T-SPOT.TB and chest X-ray. Risk factors for LTBI and history of bacillus Calmette-Guérin (BCG) vaccination were recorded. The association of T-SPOT.TB and TST results with risk factors for LTBI was tested through univariate logistic regression models. Agreement between tests was quantified using kappa statistics. Treatment for LTBI was started 1 month before anti-TNF therapy when indicated.


RESULTS
Fifty patients were included; 90% had prior BCG vaccination. A positive T-SPOT.TB was strongly associated with a presumptive diagnosis of LTBI (odds ratio 7.43; 95% confidence interval 1.38-39.9), which was not the case for the TST. Agreement between the T-SPOT.TB and TST was poor, kappa = 0.33 (SD 0.13). LTBI was detected and treated in 20% of the patients. In 20% of the cases, LTBI was not retained in spite of a positive TST but a negative T-SPOT.TB. All patients received an anti-TNF agent for a median of 56 weeks (range 20-188); among patients with a positive TST/negative T-SPOT.TB, no tuberculosis was detected with a median follow-up of 64 weeks (44-188). One case of disseminated tuberculosis occurred after 28 weeks of adalimumab treatment in a patient with LTBI in spite of treatment with rifampicin.


CONCLUSIONS
This study is the first to underline the frequency of LTBI in patients with psoriasis (20%), and to support the use of IGRA instead of the TST for its detection. Nevertheless, there is still a risk of tuberculosis under anti-TNF therapy, even if LTBI is correctly diagnosed and treated.
Laffitte
E
E
Clinic of Dermatology, University Medical Hospital, CH-1211 Geneva, Switzerland. emmanuel.laffitte@hcuge.ch
Janssens
J P
JP
Roux-Lombard
P
P
Thielen
A M
AM
Barde
C
C
Marazza
G
G
Panizzon
R G
RG
Saurat
J-H
JH
D000293:Adolescent; D000328:Adult; D000368:Aged; D000995:Antitubercular Agents / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007371:Interferon-gamma / Q000032:analysis* / Q000378:metabolism; D055985:Latent Tuberculosis / Q000175:diagnosis* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011565:Psoriasis / Q000150:complications / Q000276:immunology*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014374:Tuberculin Test / Q000379:methods*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors*; D055815:Young Adult
D000995:Antitubercular Agents; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma