Table 1.

BSRBR-AS study: baseline characteristics of biological and non-biological cohorts

	Biological cohort (n=161)	Non-biological cohort (n=416)	Difference*	95% CI
Age, mean years	42.4	47.0	−4.6	−6.6 to 2.5
Male, %	64.6	67.3	−2.7	−11.3 to 5.9
Disease duration, mean years	7.7	12.3	−4.6	−6.5 to 2.7
Current smokers, %	21.3	11.0	10.2	3.9 to 16.5
BASDAI	5.8	3.3	2.6	2.2 to 2.9
BASFI	5.4	2.7	2.7	2.3 to 3.2
BAS-G§	6.7	3.2	3.4	3.0 to 3.9
CRP (mg/dL)	2.8	2.4	0.4	−0.8 to 1.6
ASDAS	3.4	2.3	1.1	0.9 to 1.3
Physical job, %	44.8	51.0	−6.2	−3.1 to 15.5
WPAI measures (in the last 7 days)
Absenteeism, %	10.9	2.8	8.1	4.7 to 11.4
Presenteeism, %	41.0	20.6	20.4	15.9 to 24.9
Overall  work impairment, %	42.3	21.4	20.9	16.2 to 25.7
Overall activity impairment, %	51.0	24.0	27.0	22.5 to 31.4

*Difference=biological – non-biologic cohort.

ASDAS, Ankylosing Spondylitis Disease Activity Scale; BAS-FI, Bath Ankylosing Spondylitis Functional Index; BAS-G, Bath Ankylosing Spondylitis Global Disease Status; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BSRBR-AS, British Society of Rheumatology Biologics register in Axial Spondyloarthritis; CRP, C reactive protein; WPAI, Work Productivity and Activity Impairment.