Table 1

RA case definition criteria and attributes

Case definition criteria	Attributes
Age group (years)	20+, 65+
Diagnoses in hospital discharge records	0, 1+
Diagnoses in ER records	0, 1+
Diagnoses in physician records	0, 1+, 2+, 3+
Specialist physician diagnoses	0, 1+
Length of physician diagnosis observation time	never, ≤1 year, ≤2 years, ≤5 years, unlimited
≥60 days between physician diagnoses	Yes, no
Exclusion criteria A	Yes, no
Exclusion criteria B	Yes, no
RA-related medications, including steroids	0, 1+
RA-related medications, excluding steroids	0, 1+

Exclusion criteria A excluded individuals with 2+ physician diagnosis codes with a different rheumatology diagnosis than an RA diagnosis; exclusion criteria B excluded individuals for whom the RA diagnosis was not confirmed by a specialist. Note: the attributes for age group, diagnoses in physician records and length of physician diagnosis observation time are not mutually exclusive.
ER, emergency room; RA, rheumatoid arthritis.