Background/Purpose:
We aimed to compare the clinical features and treatments of children with
Enthesitis-related arthritis (ERA) from 5 pediatric rheumatology centers in
order to determine whether pediatric ERA manifests differently and/or is
treated differently based on geographical location.

Methods:
We
performed a retrospective multicenter cohort study that included subjects from
5 pediatric rheumatology centers who were diagnosed with ERA from 1989-2012. Baseline
visit for patients was defined as the first rheumatology appointment at which
the patient had enthesitis, arthritis, or symptomatic uveitis. To be included
in the study, patients had to fulfill the ILAR criteria for ERA within the
first 6 months from baseline visit. Patient data collected included the
following: demographics, clinical features, patient reported outcomes, and
medications prescribed at diagnosis and over the following 12 months. Differences across sites
were compared using the Kruskal-Wallis or chi-squared test, as appropriate.

Results:
296 children with ERA were included in the study. Patients were predominantly
male (69%) and Caucasian (83%). Median age at diagnosis was 12 years (IQR:
10-14) and 53% were HLA-B27 positive. The prevalence of arthritis and uveitis criteria
did not differ significantly across sites. The prevalence of the remaining
criteria, however, was significantly different across sites (all p<0.001): enthesitis
(range: 40-88%); sacroiliac tenderness or inflammatory lumbosacral pain (range:
10-55%); HLA-B27 positivity (range: 30-84%); onset of arthritis in a male over
6 years (range: 47-77%); and history of HLA-B27 associated disease in a
first-degree relative (range: 8-37%). The table shows medication use stratified
by site and clinical features. Overall use of DMARDs and biologics differed
significantly among sites (p<0.001 and p<0.001, respectively). Use of
biologics for arthritis (+/- enthesitis) and sacroiliitis (+/- peripheral
arthritis or enthesitis) also differed significantly among sites (p<0.001 and
p<0.001, respectively).

Conclusion:
Comparison of children with ERA from 5 pediatric rheumatology centers reveals significant
variability in the presenting features and initial treatment strategies.  The
variation in presenting features may reflect either true differences by
geographic location or differences between sites in assessment of particular
features. Biologic use was significantly different among sites for children
with arthritis and sacroiliitis. These differences highlight the need for standardized
assessments for ERA as well as comparative effectiveness studies of the
different treatment options.