Background Tuberculin skin test (PPD) or interferon gamma release assays (IGRAs) are used to detect latent tuberculosis infection. Induration of 15 mm or more is considered positive in any person whereas this cut-off is ≥5 mm for immunosuppressed individuals such as Rheumatoid arthritis. Since IGRAs are dependent on normal T-cell function, it may result in false-negatives for among RA patients due to disease itself and immunosuppressive drugs.

Objectives We aimed to compare IGRA results of RA patients using high dose DMARDS vs. not using any of them.

Methods Totally 534 RA patients among Hacettepe University Rheumatology Biologic Registry Database (HURBIO) database was enrolled into this study. QFT-Plus test of patients with rheumatoid arthritis (RA) between January 2018 and March 2021 during work up before biologic/targeted therapy were analysed, retrospectively. The patient group was divided into two according to the drugs have been using at the time of IGRA test. Patients using methotrexate ≥ 10 mg or leflunomide (any dose) or steroids (≥7.5 mg prednisolone) or any combination thereof were classified as the “High Dose” group. The other group consisted of patients who did not take these drug doses. Demographic characteristics, comorbidities, drugs and doses used, and hemogram, sedimentation, and CRP values of the patients were recorded. QuantiFERON test was recorded as positive, negative, indeterminate.

Results 353(66.1%) RA patients were in the high dose patient group and also 287(81.3%) of these patients were female, the median age was 55 years (min:19- max:82). The high dose group was older than the other group. When the two groups were compared, no statistically significant difference was found between comorbidity, and smoking (Table 1). While QFT positivity was detected in 37 (10.5%) patients in the high-dose group, it was found to be positive in 37 (20.4%) patients in the other group (p<0.001). However, there was no significant difference regarding acute phase reactants, hemogram including lymphocyte counts and IFN-gamma levels in the tubes between these two groups.

Conclusion Our results confirmed a significantly lower QFT-Plus positivity in patients with RA taking methotrexate ≥ 10 mg or leflunomide (any dose) or steroids (≥7.5 mg prednisolone). Physicians should be careful in interpretation of QFT-Plus in patients with rheumatoid arthritis. Further analysis including flow cytometry analysis is required to better identifying cut-offs for immunosuppressive individuals and patients with inflammatory rheumatic diseases.

Disclosure of Interests None declared