Table 3

Estimated difference in BASDAI or ASDAS-CRP drop following start of a first TNFi induced by different covariates after stratification for baseline CRP levels

	Difference in ΔBASDAI			Difference in ΔASDAS-CRP
	BASDAI units	95% CI	p Value	ASDAS units	95% CI	p Value
Patients with elevated baseline CRP
Smoking current vs never	0.75	0.22 to 1.28	0.005	0.69	0.30 to 1.08	0.001
Smoking former vs never	0.36	−0.28 to 1.00	0.27	0.30	−0.18 to 0.78	0.22
Female vs male	0.35	−0.17 to 0.87	0.19	0.16	−0.22 to 0.54	0.41
HLA-B27 negative vs positive	0.48	−0.19 to 1.16	0.16	0.18	−0.33 to 0.68	0.49
nr-axSpA vs AS	0.82	0.13 to 1.50	0.02	0.53	0.02 to 1.04	0.04
Education (+5 years)	−0.19	−0.57 to 0.19	0.32	−0.11	−0.39 to 0.17	0.43
Symptom duration (+10 years)	0.10	−0.19 to 0.39	0.51	0.10	−0.12 to 0.32	0.36
Age (+10 years)	−0.02	−0.30 to 0.25	0.87	−0.08	−0.29 to 0.13	0.44
BMI (+5 units)	0.24	−0.03 to 0.50	0.08	0.13	−0.07 to 0.33	0.20
Exercise yes vs no	−0.43	−0.92 to 0.06	0.09	−0.24	−0.61 to 0.12	0.19
Patients with normal baseline CRP
Smoking current vs never	0.30	−0.24 to 0.83	0.28	0.17	−0.21 to 0.56	0.38
Smoking former vs never	0.59	0.002 to 1.18	0.05	0.12	−0.31 to 0.54	0.59
Female vs male	0.37	−0.12 to 0.86	0.14	0.11	−0.25 to 0.46	0.55
HLA-B27 negative vs positive	0.20	−0.35 to 0.76	0.47	−0.16	−0.57 to 0.26	0.44
nr-axSpA vs AS	1.08	0.55 to 1.60	<0.001	0.39	−0.003 to 0.77	0.05
Education (+5 years)	−0.55	−0.96 to −0.19	0.006	−0.15	−0.45 to 0.15	0.35
Symptom duration (+10 years)	0.01	−0.28 to 0.30	0.94	−0.03	−0.25 to 0.18	0.77
Age (+10 years)	0.12	−0.15 to 0.38	0.38	0.16	−0.03 to 0.35	0.10
BMI (+5 units)	0.10	−0.17 to 0.37	0.46	−0.01	−0.20 to 0.18	0.94
Exercise yes vs no	0.18	−0.34 to 0.70	0.51	−0.001	−0.38 to 0.37	0.99

Effect size estimates of differences in ΔBASDAI and ΔASDAS-CRP (as demonstrated in figure 1C,D) are displayed for each indicated covariate. Models are adjusted for all covariates and for differences in baseline BASDAI and BASFI associate with each covariate. Positive coefficients signify a reduced anti-TNF response in terms of BASDAI and ASDAS-CRP drop.
AS, ankylosing spondylitis; ASDAS-CRP, Ankylosing Spondylitis Disease Activity Score using the C-reactive protein (CRP); BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BASFI, Bath Ankylosing Spondylitis Functional Index; BMI, body mass index; HLA, human leucocyte antigen; Nr-axSpA, non-radiographic axial spondyloarthritis; p, Wald-type p value; TNFi, tumour necrosis factor inhibitor.