Table 1. Demographics of UK and US JIA patient cohorts.

	UK cohort	US cohort
Number of cases	197	210
JIA Subtype at time of starting MTX (in %) :
Oligoarticular Persistent	9.1	8.6
Oligoarticular Extended	26.4	20.9
Polyarticular RF-	37.6	67.6
Polyarticular RF+	5.6	1.9
Enthesitis related arthritis	6.0	0
Psoriatic	2.5	0.95
Systemic	10.7	0
Unclassified	2.0	0
Female (%)	132 (67%)	164 (78%)
Median and range of disease duration at starting MTX (decimal years)	1.00, 11.53	1.08, 15.8
Median and range of age at starting MTX (decimal years)	7.93, 14.97	7.25, 18.91
Median and range of active joints at start of MTX	6, 34	8, 61
Median and range of restricted joints at start of MTX	4, 41	4, 44