Obesity and fibromyalgia are associated with Difficult-to-Treat Rheumatoid Arthritis (D2T-RA) independent of age and gender

There is still a significant proportion of patients with rheumatoid arthritis (RA) in whom multiple therapeutic lines are ineffective. These cases are defined by the EULAR criteria as Difficult-to-Treat RA (D2T-RA) for which there is limited knowledge of predisposing factors. To identify the clinical features associated with D2T-RA in real-life practice. We retrospectively collected demographic, clinical, and serological data on 458 patients consecutively seen for RA between January 2019 and January 2023. We compared patients fulfilling the D2T-RA criteria with the remaining RA cohort using univariate comparisons and logistic regression to determine the impact of clinical features, comorbidities on outcome variable, adjusted for confounders. Seventy-one/458 (16%) patients fulfilled the 2021 EULAR criteria for D2T-RA with no significant differences for age (median 62 years interquartile range -IQR- 58- 65 vs. 62 IQR 60 – 63 in non-D2T), gender prevalence (23% in both groups) and positivity rates for rheumatoid factors (62% vs. 62% in non-D2T) and Anti-Citrullinated Protein Antibodies (ACPA) (69% vs. 61% in non-D2T). Conversely, D2T-RA cases had significant longer disease duration (median 15 years IQR 13–17 vs. 10 years IQR 9–11 in non-D2T; p < 0.0001). D2T-RA also had more erosions at baseline (24% vs. 11% in non-D2T; p < 0.0001) and higher disease activity index (CDAI) at the last follow up visit (15.7 ± 10.5 vs. 7.5 ± 8.8 in non-D2T; p < 0.0001). D2T-RA cases suffered with higher frequency of obesity (33% vs. 19% in non-D2T, p = 0.021) and fibromyalgia (25% vs. 10% in non-D2T, p < 0.0001). The multivariate analysis confirmed the correlations of D2T-RA with disease duration (Odds ratio -OR- 1.06, 95% confidence interval -CI—1.03–1.09; p < 0.0001), baseline erosions (OR 2.73, 95% CI 1.28–5.82; p = 0.009), obesity (OR 2.22, 95% CI 1.10–4.50; p = 0.026) and fibromyalgia (OR 3.91, 95% CI 1.76–8.70; p = 0.001), independent of age and gender. High disease activity, baseline erosions and disease duration are significantly associated with the D2T phenotype of RA while we confirm the importance of obesity and fibromyalgia.