Risk Factors and Outcomes of Opportunistic Infections in Patients With Autoimmune Inflammatory Rheumatic Diseases: A Retrospective Comparative Study of Disease-Modifying Antirheumatic Drugs and Biologics

Background: This study aimed to compare the incidence and clinical outcomes of opportunistic infections (OIs) in patients with autoimmune inflammatory rheumatic diseases (AIIRDs) according to treatment with disease-modifying antirheumatic drugs (DMARDs) or biologics.Methods: We retrospectively analyzed 490 hospitalized patients with AIIRDs selected from 1,493 adult inpatient cases at a tertiary hospital in South Korea in 2022.Of these, 409 received DMARDs and 81 received biologics.Patients receiving both were classified as biologics users.The primary outcome was OI frequency.Results: OIs occurred in 22.9% (112/490) of hospitalized AIIRD patients, with no significant difference between DMARD and biologic users (22.5% vs. 24.7%,P = 0.772).Intensive care unit admission, organ support therapy, and mortality were numerically higher in the DMARD group but were not statistically significant.In multivariable analyses, higher Charlson Comorbidity Index and tacrolimus use were consistently associated with increased OI risk.Baseline erythrocyte sedimentation rate was independently associated with OIs in more fully adjusted models.Methotrexate showed a borderline inverse association, whereas biologic use was not independently associated with OIs.Conclusion: Among hospitalized patients with AIIRDs, OI risk appeared to be driven more by comorbidity burden, inflammatory burden, and treatment context than by drug class.These findings support individualized risk assessment and targeted prevention strategies in hospitalized AIIRD patients.