Interferon-inducible protein-10 as a marker to detect latent and active tuberculosis in rheumatoid arthritis

Abstract

SETTING: Effective tuberculosis (TB) screening should be performed before anti-tumour necrosis factor alpha (TNF-alpha) treatment in rheumatoid arthritis (RA). The usefulness of the tuberculin skin test (TST) and Quanti-FERON (R)-TB Gold (QFT-G) for detecting latent tuberculosis infection (LTBI) is limited. OBJECTIVE: We tested the diagnostic performance of interferon-gamma (IFN-gamma) inducible protein 10 (IP-10) and IFN-gamma for detecting LTBI in RA patients receiving anti-TNF-alpha treatment. DESIGN: IP-10 levels were determined by enzyme-linked immunosorbent assay in 56 RA patients and 18 active TB patients. TST was performed using the Mantoux method and QFT-G was performed by measuring IFN-gamma levels in whole blood treated with TB-specific antigens. RESULTS: Twenty-four (42.9%) TST-positive patients were defined as having LTBI. Significantly higher levels of baseline, early secretory antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) stimulated IP-10 were observed in active TB patients (median 209.9 pg/ml, 899.0 pg/ml and 880.2 pg/ml, respectively) and RA patients with LTBI (165.3 pg/ml, 904.4 pg/ml and 747.5 pg/ml, respectively), compared to those without LTBI (89.3 pg/ml, 579.4 pg/ml and 515.0 pg/ml, respectively). Baseline IP-10 has high sensitivity (83.3% and 100%) and medium specificity (67.9% and 59.6%), while ESAT-6-stimulated IP-10 has high sensitivity (87.5% and 100%) and specificity (85.7% and 71.2%) for detecting LTBI and TB. The performance of IP-10 is superior to IFN-gamma for detecting LTBI (TST+) and active TB. CONCLUSION: IP-10 may be used for detecting LTBI and as a potential biomarker to identify active TB in RA patients receiving anti-TNF-alpha treatment.