Objective: The International League of Associations for Rheumatology (ILAR) criteria constitute the current international diagnostic standard for juvenile psoriatic arthritis (PsA), replacing the less-restrictive Vancouver criteria. The impact of this change on the population diagnosed with juvenile PsA is unknown.
Methods: We reviewed the records of patients seen in a pediatric rheumatology clinic with International Classification of Diseases, Ninth Revision diagnosis codes for psoriasis, PsA, or spondylarthritis. Characteristics of children who met the Vancouver and ILAR criteria were compared.
Results: Of 139 children meeting the Vancouver criteria for juvenile PsA, ILAR criteria excluded 80 (58%). Grounds for exclusion were insufficiently definitive rash (44%), a competing diagnosis of enthesitis-related arthritis (23%), family history of psoriasis limited to second-degree relatives (16%), fulfillment of criteria for >1 subtype of juvenile idiopathic arthritis (JIA) (5%), and HLA-B27 in a male with arthritis onset after age 6 (2%). Remaining patients were not homogeneous but could be divided into younger and older subpopulations differing in clinical features as described previously among patients identified under the Vancouver standard. Of excluded patients, 76% were reclassified as having other forms of JIA yet were phenotypically comparable with those retained.
Conclusion: Despite apparently modest changes from previous criteria, ILAR definitions strikingly restrict the diagnosis of PsA in childhood. Similarity between excluded and included patients suggests that these restrictions may not reflect substantive clinical differences. To the extent that excluded patients become reclassified within JIA, current criteria risk compromising other ILAR categories while reducing the number of patients available for the study of juvenile PsA.