Effectiveness of the Combination of a Whole-blood Interferon-gamma Assay and the Tuberculin Skin Test in Detecting Latent Tuberculosis Infection in Rheumatoid Arthritis Patients Receiving Adalimumab Therapy

Objective: To investigate QuantiFERON-tuberculosis Gold (QFT-G) assay and tuberculin skin test (TST) for latent tuberculosis (TB) infection (LTBI) in patients with rheumatoid arthritis (RA) treated with adalimumab.

Methods: We prospectively followed up 43 RA patients who received adalimumab therapy and underwent serial TSTs and QFT-G assays. TST was performed using Mantoux method and QFT-G assay was examined by measuring interferon-gamma levels in whole blood samples that were incubated with early secretary antigenic target-6 and culture filtrate protein 10.

Results: Before starting adalimumab therapy, 8 RA patients (18.6%) had positive and 35 (81.4%) had negative TST results. All 8 RA patients with positive TST results were diagnosed as LTBI and received isoniazid prophylaxis (INHP) 1 month before starting adalimumab therapy. None of these 8 RA patients developed active TB 2 years after completing INHP. A high rate (10 [37.0%] patients) of TST conversion was observed among 27 patients who had completed 12-month adalimumab therapy. Of these 10 patients with TST conversion, 2 patients had positive QFT-G results and 1 developed active TB disease. Among 17 RA patients who did not have TST conversion after 12-month adalimumab therapy, 1 patient who had a positive QFT-G result developed active TB disease. Of all 43 RA patients who received adalimumab therapy, 4 (9.3%) developed active TB after starting adalimumab therapy.

Conclusion: The application of TST for detecting LTBI is limited in RA patients by the frequent presence of anergy. Combined QFT-G assay and TST can aid in detecting LTBI in RA patients receiving adalimumab therapy.