Influence of baseline modified Rheumatic Disease Comorbidity Index (mRDCI) on drug survival and effectiveness of biological treatment in patients affected with Rheumatoid arthritis, Spondyloarthritis and Psoriatic arthritis in real-world settings

Aim: To assess the impact of baseline modified Rheumatic Disease Comorbidity Index (mRDCI) a simple comorbidity count, on overall survival of treatments with biological drugs in patients affected with Rheumatoid Arthritis (RA), Spondyloarthritis (SpA) and Psoriatic Arthritis (PsA) in real-world settings. Methods: Patients (nr. 635) with RA (nr. 214), SpA (nr. 213) and PsA (nr. 208) starting a first biological drug were retrospectively analysed. mRDCI was scored at baseline, and disease characteristics were recorded at entry and at last observation. Drug retention was analysed using Kaplan-Meier curves. Cox regression models were used to estimate the association of baseline mRDCI with drug discontinuation and clinical outcomes, the achievement of clinical remission based on 28 joint-Disease Activity Score (DAS28) <2.6 for RA and PsA, and on Ankylosing Spondylitis-C-reactive protein Disease Activity Score (ASDAS-CRP) <1.3 for SpA. Results: Baseline mRDCI significantly correlated with the number of biological drug switches (rho 0.26). Persistence on biologic therapy was significantly higher in patients with mRDCI=0 (96.4%), than in those with mRDCI ≥2 (83.9%). Patients without comorbidities showed significantly higher drug survival rate in PsA (P = 0.0001) or SpA (P = 0.02), but not in RA. mRDCI was also found to be a predictor of definitive drug discontinuation (HR: 1.53) and of failure to achieve remission in RA (HR: 0.66) or PsA (HR: 0.77), and in SpA (HR: 0.43). Conclusions: This study provided evidence that baseline mRDCI negatively impacts the persistence on biologic treatments and clinical outcomes in patients with RA, SpA and PsA in real-life settings.