The authors wish to make the following correction to this paper [...].

<p>Multiple studies have shown the microbiota to be abnormal in patients with spondyloarthritis (SpA). The purpose of this study was to explore the genetic contributions of these microbiota abnormalities. We analyzed the impact of HLA-B27 on the microbiota of children at risk for SpA and compared the microbiota of HLA-B27+ pediatric offspring of ankylosing spondylitis (AS) patients with that of HLA-B27+ children with SpA. Human DNA was obtained from the offspring for determination of HLA-B27 status and polygenic risk score (PRS). Fecal specimens were collected from both groups for sequencing of the V4 region of the 16S ribosomal RNA gene. Among the offspring of AS patients, there was slight clustering by HLA-B27 status. After adjusting for multiple comparisons, five operational taxonomic units (OTUs) representing three unique taxa distinguished the HLA-B27+ from negative children: and were lower in the HLA-B27+ offspring, while was higher. HLA-B27+ offspring without arthritis were compared to children with treatment-naïve HLA-B27+ SpA. After adjustments, clustering by diagnosis was present. A total of 21 OTUs were significantly associated with diagnosis state, including (higher in SpA patients) and (higher in controls). Thus, our data confirmed associations with and with juvenile SpA, and also suggest that the mechanism by which HLA-B27 is associated with SpA may not involve alterations of the microbiota.</p>

<p><strong>OBJECTIVE: </strong>To characterize the effect of anti-tumor necrosis factor (TNF) therapy compared to conventional synthetic disease-modifying antirheumatic drugs (csDMARD) in children with enthesitis-related arthritis (ERA) over the first year after diagnosis.</p>

<p><strong>METHODS: </strong>We conducted a multicenter retrospective comparative effectiveness study of children diagnosed with ERA. We estimated the effect of anti-TNF therapy on clinical variables (active joint count, tender entheses count) and patient-reported pain and global assessment of disease activity over the first year after diagnosis using state-of-the-art comparative effectiveness analytic methods.</p>

<p><strong>RESULTS: </strong>During the study period, 217 patients newly diagnosed with ERA had a total of 965 clinic visits the first year after disease diagnosis. Children [median age 11.6 yrs, interquartile range 10-14] were treated with anti-TNF monotherapy (n = 33, 15.2%), csDMARD monotherapy (n = 73, 33.6%), or both (n = 52, 23.9%) in the first year after disease diagnosis. There was a statistically significant improvement in the primary outcome, active joint count, over time in children who received an anti-TNF drug versus those who did not (p = 0.03). Additionally, use of anti-TNF therapy versus no anti-TNF therapy was associated with less patient-reported pain (p &lt; 0.01) and improved disease activity over time as assessed by the clinical Juvenile Arthritis Disease Activity Score (p &lt; 0.01). The magnitude of estimated effect on clinical outcomes was uniformly greater, with the exception of tender entheses count, in children treated with an anti-TNF drug versus a csDMARD.</p>

<p><strong>CONCLUSION: </strong>During the first year after diagnosis, anti-TNF exposure was associated with benefits for several clinically meaningful outcomes in children with enthesitis-related arthritis.</p>

<p><strong>BACKGROUND: </strong>Enthesitis-related arthritis (ERA) is a specific subtype of juvenile idiopathic arthritis (JIA) defined according to the International League of Associations for Rheumatology (ILAR) criteria. We aimed to characterize the clinical features and treatment regimens in an inception cohort of children with ERA.</p>

<p><strong>METHODS: </strong>We performed a retrospective, cross-sectional, multicenter cohort study including subjects diagnosed with ERA between 1989 and 2012. Patients all fulfilled the ILAR criteria for ERA within 3&nbsp;months of initial presentation to the rheumatology clinic. Differences in the prevalence of clinical criteria across study sites and by human leukocyte antigen (HLA)-B27 status were assessed using the Wilcoxon rank-sum or chi-square test, as appropriate.</p>

<p><strong>RESULTS: </strong>Two hundred thirty-four children met the inclusion criteria. Their median age at diagnosis was 11.6&nbsp;years, and 59% were HLA-B27-positive. Sixty-nine percent had enthesitis and arthritis at the time of diagnosis. Seventy-eight percent had a pauciarticular onset. The prevalence of all ILAR criteria at diagnosis, except arthritis and acute anterior uveitis, differed significantly across sites (all p &lt; 0.01). Medication use varied significantly across sites for children with peripheral arthritis (p &lt; 0.001), but not for sacroiliitis or enthesitis only. Nonsteroidal anti-inflammatory drugs and disease-modifying antirheumatic drugs were the most commonly prescribed treatments, with anti-TNF agents primarily being initiation for sacroiliitis. HLA-B27 positivity was associated with male sex, higher active joint count, sacroiliitis, and higher disease activity at disease onset.</p>

<p><strong>CONCLUSIONS: </strong>The majority of children had a pauciarticular onset, and several statistically significant clinical differences based on HLA-B27 status were identified. The observed heterogeneity in clinical presentation across sites reflects either true differences in patient populations or differences in how the ILAR criteria are being applied.</p>

<p><strong>OBJECTIVE: </strong>To develop and validate the Juvenile Spondyloarthritis Disease Activity Index (JSpADA) for use in clinical practice and research.</p>

<p><strong>METHODS: </strong>Using modified Delphi consensus techniques, 10 items were selected by participants in the international pediatric rheumatology listserv, the Childhood Arthritis and Rheumatology Research Alliance, and the listserv for the pediatric section of the American College of Rheumatology. Validation was performed in a retrospective multicenter cohort of 244 children.</p>

<p><strong>RESULTS: </strong>In total, 106 physicians representing 14 countries completed the initial questionnaire. Completion rates for the subsequent questionnaires were 84%, 75%, and 77% of the original respondents. Ten items exceeded 80% consensus: arthritis, enthesitis, patient pain assessment, inflammatory markers, morning stiffness, clinical sacroiliitis, uveitis, back mobility, and patient and physician assessments of disease activity. After item analysis, 2 items were eliminated (patient and physician assessments of disease activity). Factor analysis identified 3 primary domains that explained 58% of the variance: peripheral disease, axial disease, and uveitis. The Cronbach's α coefficient was 0.66. The JSpADA had high or moderate correlations with the Juvenile Arthritis Disease Activity Score (r = 0.81), patient and physician assessments of disease activity (r = 0.70 and r = 0.66, respectively), and the Childhood Health Assessment Questionnaire (r = 0.56). The JSpADA discriminated well between subjects with active versus inactive disease (P &lt; 0.001) and was responsive to improvement or worsening in disease activity over time (P &lt; 0.001).</p>

<p><strong>CONCLUSION: </strong>Using international input and consensus formation techniques, we developed and validated the first disease activity assessment for juvenile spondyloarthritis. Future studies should validate the JSpADA in a prospective multicenter cohort.</p>