Influence of obesity, age, and comorbidities on the multi-biomarker disease activity test in rheumatoid arthritis

Traditional markers of inflammation are often required for inclusion in rheumatoid arthritis trials, yet patients with active disease may have normal lab tests. The potential use of the multi-biomarker disease activity (MBDA) test in this setting is unclear, as is understanding of whether it is influenced by patient characteristics (e.g., age, BMI, and comorbidities).

Using data from the Corrona registry, we conducted a cross-sectional analysis of RA patients with MBDA tests. Patients were classified as low (<30), moderate (30-44, and high (>44) and by clinical and RA-related factors. Regression was used to evaluate the association between MBDA score and age, body mass index, comorbidities, and RA-related factors.

Of 357 eligible patients, 76% (n = 273) had normal CRP (<10mg/L) with high (33%), moderate (45%), and low (22%) disease activity by MBDA. The MBDA score was significantly associated with BMI, age, CDAI, and SJC. There was no association between MBDA score and fibromyalgia, diabetes, smoking, or COPD; none were confounders between MBDA score and either SJC or CDAI. For patients in CDAI remission, older age (2.6 units per decade; p = 0.03) and obesity (β = 10.5 for BMI > 30, referent to <25; p = 0.02) were independently associated with MBDA score. An adjusted MBDA score was proposed that was highly correlated with the original MBDA (r = 0.91).

In this real-world analysis, the MBDA score was associated with RA disease activity, obesity, and age, and was negligibly affected by common comorbidities. Almost one-third of patients with normal CRP had high MBDA scores. An adjustment to the MBDA score to account for body mass index and age is proposed.