Background/Purpose: The Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry began enrolling children with juvenile idiopathic arthritis (JIA) in July 2015. The large number of children with prevalent JIA in the Registry provides a unique opportunity to study longitudinal medication use in clinical practice, including the use of methotrexate (MTX).

Methods: Participants were enrolled at 55 centers in the US and Canada. Children with the following characteristics were eligible for enrollment in the Registry: 1) new diagnosis JIA; 2) systemic JIA; 3) history of ≥ 5 joints involved during disease course; 4) children newly starting or re-starting MTX or biologic. Data were obtained from Registry medication logs that contain the patient’s complete medication use history, including start and stop dates. Children were included in this analysis if they were ≥ 12 months since JIA diagnosis and treated with MTX.  Patient date of diagnosis and medication start and stop dates were imputed if month or day were missing. Median and IQR for time to initiation of biologic therapy was calculated for those patients who started a biologic >= 60 days after MTX, in order to exclude those who were intended to have initial therapy with combination biologic and MTX therapy.

Results: Nine hundred and three children were included in the analysis (Table 1). Median time between diagnosis and initiation of MTX was 61 days (IQR: 0-461) and was similar for those initially started on oral (PO) and those initially started on subcutaneous (SQ).  Forty-four percent of children received their initial MTX as PO. Children with extended oligoarthritis had the lowest proportion of initial PO MTX (26%) and children with polyarticular JIA RF+ had the highest percentage (56%).  Among children started on initial PO MTX, 31% switched to SQ during their follow-up. Among children started on initial SQ MTX, 25% switched to PO. Median time to initial biologic therapy among those receiving initial PO MTX was 304 days (IQR: 142-731) and 250 days (IQR: 122-813) for those receiving initial SQ MTX.

Conclusion: Among this large cohort of children with JIA, route of initial MTX therapy was relatively evenly divided between SQ and PO and switching between routes was common. Patients started on SQ MTX had a somewhat shorter time to initiation of biologic therapy. Additional analyses will evaluate the associations between initial route of MTX, patient characteristics, and clinical outcomes.

Table 1. Methotrexate use and route of administration

PO: oral; SQ: subcutaneous