A 24-week observational study found that a combination of the cellular biomarkers—lymphocyte count (LC) and plasmablast frequency—helps identify patients with rheumatoid arthritis (RA) who will not benefit from rituximab (Rituxan) with high probability, according to data from an Austrian Rituximab registry. The findings were published online in Arthritis Research & Therapy.
Data from the registry were used to identify 44 RA patients who were receiving rituximab for the first time, and for whom complete data on T- and B-cell cytometry were available. Patients were classified according to European League Against Rheumatism (EULAR) as good responders, moderate responders, or nonresponders. Low disease activity (LDA) was defined as disease activity score in 28 joints (DAS28) ≤3.2.
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At week 24, there were 33 patients (75%) classified as EULAR responders and 15 patients (34%) had achieved remission or LDA. Researchers analyzed baseline levels of lymphocyte subsets between responders and nonresponders to rituximab therapy and found that total LC was significantly higher in the nonresponder group compared with patients with EULAR response (2681 µL vs 1956 µL, respectively). However, there was no significant difference in baseline LC according to whether LDA was achieved at 24 weeks. At baseline among lymphocyte subsets, none of these populations was significantly different between patients with a DAS28 >3.2 or a DAS28 ≤3.2 at week 24, which was also true for plasmablast frequency, previously identified as a predictor of EULAR response.
These two biomarkers had a high negative predictive value and sensitivity to identify patients who will not achieve LDA under rituximab at 24 weeks, with a sensitivity of 93.3% and a specificity of 44.8%. Additionally, the combination was superior to using either biomarker independently, said the researchers noting that in clinical practice this is particularly crucial for treatment decisions, where the target of treatment is remission or at least LDA.
