High rates of tuberculin skin test positivity due to methotrexate therapy: False positive results?

RATIONALE: The tuberculin skin test (TST) and interferon ? release assays (IGRAs) are commonly used for latent tuberculosis infection (LTBI) screening. Unexpectedly high TST positivity rates have been reported in patients with rheumatic diseases, and methotrexate is frequently used in this population. We hypothesized that methotrexate use could be associated with false-positive TST results. OBJECTIVES: To investigate whether treatment with methotrexate and other factors are associated with false-positive TST results in patients with rheumatic diseases. METHODS: Prospective single-center study conducted between April 2013 and March 2016. Adult patients with rheumatic diseases were evaluated with a TST and two IGRAs for LTBI screening. We compared TST and IGRA results in patients treated and not treated with methotrexate and analyzed for factors associated with positive TST results. CONCLUSIONS: Our data suggest false-positive TST results associated with methotrexate therapy. Thus, we recommend against using the TST for LTBI screening in patients receiving methotrexate and the preferential use of IGRAs in such patients. MEASUREMENTS AND MAIN RESULTS: We studied 393 patients with rheumatic diseases, including ankylosing spondylitis (ASP, n = 90), rheumatoid arthritis (RA; n = 120), psoriatic arthritis (PA, n = 126), and other disorders (n = 57). The rate of TST positivity varied across the groups: ASP 22.2%, RA 25%, PA 35.7%, and other disorders (22.8%). Positivity rates were lower with IGRAs. Methotrexate use was associated with a statistically significant two-fold increase in the risk of a positive TST and a dose\x96 response relationship was observed. We found no statistically significant associations between methotrexate use and IGRA test positivity.

Rituximab for remission induction and maintenance in refractory granulomatosis with polyangiitis (Wegener's): ten-year experience at a single center.

OBJECTIVE: This study was conducted to evaluate the efficacy and safety of repeated and prolonged B cell depletion with rituximab (RTX) for the maintenance of long-term remission in patients with chronic relapsing granulomatosis with polyangiitis (Wegener's) (GPA). METHODS: We conducted a single-center observational study of all patients with chronic relapsing GPA treated with at least 2 courses of RTX between January 1, 2000 and May 31, 2010. Participants in the Rituximab in ANCA-Associated Vasculitis (RAVE) trial were excluded from this analysis. Data were abstracted from electronic medical records. RESULTS: Fifty-three patients with refractory GPA (median age 46 years [interquartile range (IQR) 30-61 years]; 53% women) received at least 2 courses of RTX to treat GPA relapses or to maintain remission. All but 1 patient had antineutrophil cytoplasmic antibodies (ANCA) against proteinase 3 (PR3). These patients received a median of 4 courses of RTX (IQR 3-5); all had depletion of B cells, and the median time to return of B cells was 8.5 months (IQR 6-11 months). All observed relapses occurred after reconstitution of B cells and were accompanied or preceded by an increase in ANCA levels, except for the 1 ANCA-negative patient. Infusion-related adverse events occurred in 16 patients. During the period of B cell depletion, 30 infections requiring antimicrobial therapy were recorded. CONCLUSION: RTX appeared to be effective and safe for the induction and maintenance of remission in patients with chronic relapsing GPA. Repeated depletion of B lymphocytes seems to be associated with a low risk of infections. Preemptive re-treatment decisions can be individualized based on serial B lymphocyte and PR3 ANCA monitoring. The use of RTX for the maintenance of long-term remission merits further formal investigation.