Background/Purpose:

Enthesitis Related Arthritis (ERA) is a common subtype (36%) of Juvenile Idiopathic Arthritis (JIA) seen in India ¹. These criteria do not distinguish between axial and peripheral arthritis. The new ASAS criteria ^2,3do, and have to date been applied only to the adult population. This distinction is important from both the diagnostic and therapeutic viewpoint. Therefore, we applied the ASAS criteria to our ERA patients. This is the first study of its kind.

1. Agarwal et al. 110 patients with Enthesitis Related Arthritis: a demographic and clinical study from a tertiary level pediatric rheumatology centre in India.THU0321; EULAR 2012.
2. Rudwaleit M, et al. The ASAS classification criteria for peripheral SpA. Ann Rheum Dis; 2011; 70(1):25-31.

3. van der Heijde Dse et al. 2010 Update of the international ASAS recommendations for the use of anti-TNF agents in axial SpA. Ann Rheum Dis.2011;70(6):905-8.

Methods:

Data on JIA patients at our centre is collected on detailed proformas at onset and thereafter quarterly. All ERA patients seen over a three year period from May 2009-12 were included. ASAS axial and peripheral spondyloarthritis (SpA) criteria were retrospectively applied to this cohort, taking all features within 6 months of disease onset.

Results:

ERA:  124 children were identified, 102 were boys. Median age of onset was 10.9 years; median delay to diagnosis 5months. ERA features: 64 had arthritis and enthesitis; 60 had Enthesitis or Arthritis with  ≥ 2 of the following: SI tenderness and/or inflammatory spinal pain 28%, HLA-B27 97.6%, Family history of medically confirmed HLA-B27-associated disease 9.7%, Anterior uveitis 16.1%, Onset of arthritis in a boy after 6 yr of age 83.8%.

ASAS criteria: All 124 ERA patients could be classified per the ASAS criteria. The prevalence of each item is in Table1. No patient in this cohort had isolated inflammatory back pain (IBP) without any other feature of SpA. Thirty five children had axial and 89 peripheral SpA. Only 1 patient had imaging evidence of sacroiliitis with no back pain. All children in this study with axial complaints had IBP.

 Additional data:97.6% patients were HLAB27 positive, 19.4% had hip disease and 28.2% of SI joint MRIs were positive. A further 12 patients developed new onset inflammatory back pain over the observation period of 3 years.

 Table 1

SpA features	Axial SpA	Axial SpA	Peripheral SpA	Peripheral SpA
	Low back pain >3months + Sacroiliac imaging + ≥1 SpA feature n=29	Low Back Pain + HLAB27 + ≥ 2 SpA features n=6	Arthritis or Enthesitis or Dactylitis + ≥1 SpA feature n=88	Arthritis or Enthesitis or Dactylitis + ≥2 SpA feature n=1
IBP	29 (100%)	6 (100%)	NA	NA
Arthritis	25 (86.2%)	5 (83.3%)	88 (100%)	1 (100%)
Enthesitis (heel)	9 (31%)	0 (0%)	NA	NA
Uveitis	3 (10.3%)	1 (16.67%)	16 (18.18%)	NA
Dactylitis	0 (0%)	0 (0%)	3 (3.4%)	0 (0%)
Psoriasis	0 (0%)	0 (0%)	0 (0%)	NA
Crohn’s/Ulcerative Colitis	1 (3.4%)	1 ( 16.67%)	1 (1.13%)	NA
Good response to NSAIDs	23 (79.3%)	5 (83.33%)	NA	NA
Family h/o SpA	7 (24%)	0 (0%)	NA	0 (0%)
HLAB27	29 (100%)	6 (100%)	87 (98.86%)	NA
Elevated ESR*	20 ( 69%)	4 (100%)	NA	NA
Preceding infection	NA	NA	6 (6.81%)	NA
SI imaging	NA	NA	5 (5.68%)	NA
Enthesitis (any)	NA	NA	46 (52.27%)	0 (0%)
IBP ever	NA	NA	NA	0 (0%)

*CRP replaced by ESR

Conclusion:

The ASAS axial and peripheral SpA criteria can be applied to all children with ERA and have a sensitivity of 100%, peripheral SpA is 2.5 times as common as the axial SpA. Thus in the pediatric population the entry criteria should be peripheral and not axial disease. This has important implications for deciding therapeutic pathways in children with axial or peripheral disease and gives an oppurtunity to childen with SpA to be recruited into clinical trials  with same diagnostic criteria as for adults. We plan to expand the application of these criteria to the undifferentiated and psoriatic arthritis categories of JIA as well.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/diagnostic-value-of-the-assessment-of-spondyloarthropathy-international-society-asas-criteria-for-children-with-enthesitis-related-arthritis-era-a-single-center-study-of-124-patients/