The CorEvitas RA Registry (formerly CORRONA) is an ongoing, observational clinical registry, established in 2001 in the USA. Longitudinal follow-up data are collected from patients and their rheumatologists during routine clinic visits (approximately every 6 months) using specific CorEvitas RA questionnaires. As of October 31, 2022, more than 200 sites throughout the USA, involving around 1000 physicians, have been involved in data collection. Data from almost 60,000 patients with RA, representing over 225,000 patient years of data, are accessible in the CorEvitas RA database [19,20,21]. Data include patient visits from April 5, 2016 to October 31, 2022. To be included in the registry, patients of either sex aged 18 years or older had to be diagnosed with RA by a rheumatologist, and be currently receiving a US Food and Drug Administration (FDA)-approved biologic, biosimilar, or Janus kinase (JAK) inhibitor for RA initiated within 365 days of enrollment. Temporary treatment interruptions of less than 180 days were permitted. All patients provided written informed consent.

Patients were excluded from the registry if they had been diagnosed with any other autoimmune inflammatory arthritis; had begun RA treatment with only a non-eligible medication (including conventional synthetic disease-modifying antirheumatic drugs [csDMARDs] and prednisone); or were participating or planned to participate in a clinical trial of another RA therapy.

The study was performed in accordance with the Declaration of Helsinki and the Guidelines for Good Pharmacoepidemiology Practice (GPP). All participating investigators were required to obtain full board approval for conducting noninterventional research involving human subjects with a limited dataset. Sponsor approval and continuing review was obtained through a central institutional review board (IRB), the New England Independent Review Board (NEIRB; no. 120160610). For academic investigative sites that did not receive authorization to use the central IRB, full board approval was obtained from their respective governing IRBs, and documentation of approval was submitted to CorEvitas, LLC before the site’s participation and initiation of any study procedures. All patients in the registry were required to provide written informed consent and authorization before participating.

To be included in this study, patients must have initiated IFX-dyyb (defined as first ever use of IFX-dyyb) at the registry enrollment visit or at a follow-up visit from April 2016 onward, have follow-up data for a 6-month clinic visit (3–9 month window), and have Clinical Disease Activity Index (CDAI) scores recorded at baseline and the 6-month follow-up visit. Baseline was defined as the first visit of IFX-dyyb initiation unless it was initiated between visits, in which case baseline was the visit prior to initiation (within 4 months).

The primary outcome was the proportion of patients with moderate or high disease activity (CDAI > 10) at baseline who achieved low disease activity (LDA; CDAI ≤ 10) at 6 months following IFX-dyyb initiation.

Secondary outcomes included the proportion of patients achieving remission (CDAI ≤ 2.8) at 6 months in those with LDA, moderate or high disease activity (CDAI > 2.8) at baseline, as well as change from baseline to 6 months in CDAI, Health Assessment Questionnaire (HAQ), and patient-reported outcomes (PROs) of pain and fatigue; achievement of modified American College of Rheumatology (mACR) [22] 20/50/70 response at 6 months (≥ 20%, 50%, and 70% improvement).

Frequencies and counts were used to summarize reasons for initiation of IFX-dyyb. Reasons were categorized as follows: safety (infection, lymphoma/malignancy, toxicity, serious and minor side effect); efficacy (lack of efficacy, disease flare, active disease, primary or secondary loss of efficacy, inadequate initial response, failure to maintain initial response); cost/insurance (lack of insurance); other reason (patient preference, fear of future side effect, frequency of administration, temporary interruption, to improve tolerability, and other).

Patient data were stratified according to RA treatment prior to IFX-dyyb initiation, which included (a) previous biologic/targeted synthetic disease-modifying antirheumatic drug (tsDMARD)-naïve, (b) switched from IFX-REF or IFX biosimilar, or (c) switched from a non-IFX biologic or tsDMARD.

Descriptive statistics were used for demographic, clinical characteristics, medication use, comorbidities, and clinical assessments and outcomes at 6 months. Categorical variables were summarized using frequency and percentages. Continuous variables were summarized by number of observations, mean, standard deviation (SD), or 95% confidence intervals (CI). For patients discontinuing IFX-dyyb before the 6-month visit, outcome data were imputed via last observation carried forward, using only registry visits that occurred before discontinuation.