Arthritis & Rheumatism, Volume 60,
October 2009 Abstract Supplement

The 2009 ACR/ARHP Annual Scientific Meeting
Philadelphia October 16-21, 2009.


Utility of An Interferon-Gamma-Release Assay to Detect Latent Tuberculosis in Patients Evaluated for Immunosuppressive Therapy with Biologic Agentsa Retrospective Analysis of Routine Clinical Practice in a Low-Prevalence Population

Ehrenstein1,  Boris, Nessyt1,  Felix, Hartung2,  Wolfgang, Meyringer2,  Rotraud, Fleck2,  Martin

University Medical Center Regensburg, Regensburg, Germany
Asklepios Klinikum Bad Abbach, Bad Abbach, Germany

Purpose:

Screening for latent tuberculosis infection (LTBI) utilizing tuberculin skin test (TST) and chest x-ray (CXR) is mandatory prior to initiating TNF-alpha inhibitors and recommended before initiating other immunosuppressive therapies. Pilot studies suggested better sensitivity and specificity for detecting LTBI of interferon-gamma-release assays (IGRA) compared with TST and CXR in this setting. We aimed to evaluate the diagnostic gain of performing an IGRA in addition to standard screening with TST and CXR in routine clinical practice.

Method:

Evaluation for LTBI by TST, CXR and additionally by a commercially available IGRA was introduced in routine clinical practice from April 2008 for all inpatients of a referral tertiary-care facility specializing in rheumatic diseases. A retrospective chart review was performed for all patients receiving IGRA testing as part of diagnostic workup prior to commencing biologic immunosuppressive therapy from April to December 2008.

Results:

205 patients with rheumatic diseases (rheumatoid arthritis n=125; spondyloarthritis n=46; psoriatic arthritis n=19; other n=15) received IGRA testing as part of evaluation for LTBI before initiating biologic immunosuppression. Of the 205 IGRA, 19 (9%) were positive, 168 (82%) negative and 18 (9%) indeterminate. Among the 19 patients with LTBI detected by IGRA, only 3 had a positive TST result (of 16 evaluated), 1 had signs suggestive of LTBI in the CXR (of 16 evaluated), and 5 patients reported risk factors for LTBI (of 17 with sufficient information). Utilizing only results of TST and CXR, 14 (74%) of the 19 patients with LTBI diagnosed by IGRA would have been missed. Only 7 of 158 (4%) performed TST were positive: 4 of those had also a positive IGRA; 2 had no other evidence of LTBI, including a negative IGRA; 1 had classical signs of LTBI by CXR, reported a direct exposure to active tuberculosis, but had a negative IGRA. Indeterminate IGRA results occurred more frequently among patients pre-treated with corticosteroids at doses above 10 mg/d prednisolone-equivalent (8/33, 24%) than among patients who were untreated or pre-treated with lower doses (10/172, 6%), p<0.001 by Chi2 test.

Conclusion:

Performing only TST and CXR would have failed to detect nearly three quarters of patients with LTBI diagnosed by IGRA. The rates of false-negative IGRA- (0.5%) and false-positive TST-results (1.0%) were both low. Despite IGRA outperforming TST, it remains unclear whether outright replacement of TST with IGRA is justified. However, our data strongly support augmentation of TST with IGRA to detect LTBI.

To cite this abstract, please use the following information:
Ehrenstein, Boris, Nessyt, Felix, Hartung, Wolfgang, Meyringer, Rotraud, Fleck, Martin; Utility of An Interferon-Gamma-Release Assay to Detect Latent Tuberculosis in Patients Evaluated for Immunosuppressive Therapy with Biologic Agentsa Retrospective Analysis of Routine Clinical Practice in a Low-Prevalence Population [abstract]. Arthritis Rheum 2009;60 Suppl 10 :980
DOI: 10.1002/art.26057

Abstract Supplement

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