Table 2. Radiological and biological characteristics of the population.

MRI: magnetic resonance imaging; ESR: erythrocyte sedimentation rate; CRP: C-reactive protein; * p value ≤ 0.05

Parameters	Early-onset SpA (N=163)	Late-onset SpA (N=31)	p
Sacroiliitis on X-ray N(%)	128 (78.5)	27 (87.1)	0.85
Sacroiliitis on MRI	35(21.4)	4 (12.9)	0.75
Syndesmophytes N (%)	57 (34.9)	14 (45.1)	0.29
Enthesitis N (%)	96 (58.8)	19 (61.2)	0.80
Synovitis N (%)	111 (68.1)	23 (74.2)	0.50
Coxitis N(%)	73 (44.7)	6 (19.35)	0.008*
ESR (mm)	39.16	39.73	0.92
CRP (mg/l)	35.50	36.84	0.90
HLA-B27	16 (9.81)	2 (6.45)	0.30
Vitamin D (ng/ml)	21.58	19	0.69