An administrative data validation study of the accuracy of algorithms for identifying rheumatoid arthritis: the influence of the reference standard on algorithm performance

Table 2 Clinical characteristics and drug exposures for RA patients

Characteristics	Aged 20 and older n = 69
Age (years), mean (SD)	61.9 (13.7)
Female gender	64%
Diagnosis provided by a Specialist	86%
Morning Stiffness	65%
Hand joint involvement (>1 swollen wrist, MCP, or PIP joint)	67%
Symmetric Arthritis (PIPs, MCPs, or MTPs)	65%
Rheumatoid Nodules	19%
Radiographic changes typical of RA	22%
2-10 medium-large joint involvement (shoulders, elbows, hips, knees, ankles)	39%
1-3 small joint involvement (MCPs, PIPs, 2^nd-5^th MTPs, thumb IPs, wrists)	54%
4-10 small joint involvement (as above)	51%
>10 joint involvement (as above)	26%
RF or ACPA positive	39%
Elevated ESR or CRP	45%
NSAID/COXIB use*	77%
Glucocorticosteroid use (Oral, inter-articular or intramuscular)*	61%
DMARD use*	80%
Biologic use*	17%

*Prescribed by any physician (specialist or primary care physician).
Abbreviations: MCPs metacarpophalangeal joints, PIPs proximal interphalangeal joints, MTPs metatarsophalangeal joints, IPs interphalangeal joints, DMARD disease-modifying anti-rheumatic drug, NSAID non-steroidal anti-inflammatory drug, COXIB COX-2 selective inhibitor, RF Rheumatoid Factor, ACPA anti–citrullinated protein antibody, ESR erythrocyte sedimentation rate, CRP C-reactive protein.