Table 3

Assessment of possible effect modifiers on the relation of BMI on CRP in the whole population (428 patients), and on the relation of BMI on ASDAS-CRP in axSpA patients (168 patients) by linear regression modelling

CRP
n=428 (whole population)	β	SE	95% CI	p Value
BMI	1.14	1.30	−1.41 to 3.70	0.38
Age	0.78	2.52	−4.16 to 5.73	0.76
BMI x age	−1.02	1.72	−4.41 to 2.36	0.55
BMI	−6.12	2.86	−11.74 to −0.50	0.03
Gender	−5.49	2.50	−10.40 to −0.58	0.03
BMI x gender	4.01	1.68	0.70 to 7.32	0.02
ASDAS-CRP
n=168 (axSpA population)	β	SE	95% CI	p Value
BMI	0.31	0.22	−0.12 to 0.74	0.16
Age	0.15	0.42	−0.69 to 0.98	0.73
BMI x age	−0.17	0.31	−0.77 to 0.43	0.58
BMI	0.29	0.48	−0.65 to 1.23	0.54
Gender	0.25	0.42	−0.57 to 1.07	0.54
BMI x gender	−0.05	0.30	−0.64 to 0.55	0.88

p Value in bold: with statistical significance.
x=interaction term.
ASDAS, Ankylosing Spondylitis Disease Activity Score; axSpA, axial spondyloarthritis; BMI, body mass index; CRP, C reactive protein; β, unstandardised β coefficient.