Performance of systemic juvenile idiopathic arthritis classification criteria: One-center experience in Libya

Systemic juvenile idiopathic arthritis (sJIA) is an autoinflammatory disorder often presenting with prominent systemic features before arthritis develops. Classification criteria for sJIA have evolved, yet their comparative performance-especially in paediatric populations-remains underexplored in real-world settings. To evaluate and compare the performance of three classification criteria-ILAR (2004), PRINTO/ACR (2021), and Yamaguchi-in a paediatric cohort with suspected sJIA, with a focus on early diagnosis in the pre-arthritic phase. A retrospective cohort study was conducted at Tripoli Children's Hospital, Libya, including 38 patients treated for systemic inflammation between 2005 and 2020. Demographic, clinical, and laboratory data were extracted from medical records. Patients were classified according to ILAR, PRINTO/ACR, and Yamaguchi criteria. Agreement analysis, sensitivity, specificity, positive and negative predictive values, and kappa statistics were calculated, using PRINTO as the reference standard. The median age was 7.5 years (IQR 3.1-9.9), with nearly equal sex distribution. All patients presented with fever, 78.9% had evanescent rash, and 92.1% had arthritis at presentation. Yamaguchi criteria were met by only 36.8% of patients, showing poor sensitivity (36.1%) and agreement with PRINTO (κ = 0.036). ILAR criteria were fulfilled by 92.1%, but were missed in all three patients without arthritis. PRINTO criteria captured 94.7%, including one pre-arthritic case missed by ILAR. ILAR demonstrated high sensitivity (97.2%) and specificity (100%) against PRINTO, while Yamaguchi performed poorly across all metrics. The Yamaguchi criteria are inadequate for classifying paediatric sJIA. While ILAR criteria remain specific, they risk delaying diagnosis in periarthritis presentations. The PRINTO/ACR 2021 criteria offer a more sensitive and clinically useful framework for early classification of sJIA, supporting their adoption in paediatric practice to facilitate timely diagnosis and intervention.