Background/Purpose: Among JIA children with Enthesitis related arthritis (ERA) category have more pain, poorer health status and are less likely to achieve or maintain sustained remission. There has been paucity of instruments to measure disease activity in ERA and recently the Juvenile Spondyloarthritis Disease Activity Index (JSpDA) was developed. We planned to prospectively validate JSpDA and compare its performance with other disease activity scores used in children and adults.

Methods:

Children with ERA (ILAR criteria) less than 18 years of age were enrolled. Baseline characteristics and different disease activity measures (JSpDA, BASDAI, ASDAS-ESR, JADAS-10) and C-HAQ were recorded at baseline and on follow up after at least 3 months of follow up. At both visits physician global assessment and patient global assessment was recorded on the scale of 0-10. Construct validity was tested using JADAS-10, physician global assessment, patient global assessment and C-HAQ. Correlation of JSpDA and different disease activity scores was done. Internal consistency was evaluated using peripheral arthritis score. Discriminative validity was evaluated using the physician global assessment.

Results:

The mean age of 125 children (114 boys) was 14.2+2.23 years. The mean disease duration was 34.8+28.04 months. Eighty nine children had persistent disease while 31 had episodic disease and 5 children had less than 3 months of disease. Eighty eight of 102 (86%) children were HLA-B27 positive. Seventy seven (61.6%)) children had inflammatory back pain ever and 43% had radiographic sacroiliitis. 113 had peripheral arthritis ever (90.4%) and eighty two (65%) at the time of recruitment.

Among 125 patients 91 were taking NSAIDs and 28 were taking synthetic DMARDs (Methotrexate=19, sulfasalazine=8, Leflunomide=1). Mean disease activity score were, JSpDA: 3.07+1.84, JADAS10: 12.43+8.58, BASDAI:3.06+2.3 ASDAS ESR: 3.01+1.24. Mean C-HAQ was 0.75 +0.65.

JSpDA showed high correlation with JADAS-10 (r=0.874) and PGA (r= 0.875) and moderate to high correlation with C-HAQ (r=0.733). Hence demonstrated good construct validity. Correlation between peripheral disease component and total score was 0.96, showing good internal consistency. The mean JSpDA scores for children with a physician global assessment (PGA) on visual analog scale score of 0 (n =19) & >0 (n=105) were 0.31 and 3.6 respectively (p< 0.001) hence showing good discriminative validity.

37 children had a follow up visit at least 3 months later, disease activity increased in 21, decreased in 13 & did not change in 3. Mean change in JSpDA was significantly different among those who improved [+2.29+0.57] when compared to who worsened [-1.67+0.48; (p<0.001)], showing good sensitivity to change.

JSpDA also showed highly correlation with other scores like JADAS10 (r=0.87) and BASDAI(r=0.83), ASDAS ESR(r=0.85). Adult score showed moderate to high correlation with PGA [ASDAS ESR(r=0.87), BASDAI (r=0.77)] and moderate with C-HAQ [ASDAS ESR(r=0.77), BASDAI (r=0.68)]

Conclusion: JSpDA is a valid score for measuring disease activity in ERA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prospective-validation-of-the-juvenile-spondyloarthritis-disease-activity-index-and-its-comparison-with-adult-spondyloarthritis-disease-activity-scores/