Table 1.

Sociodemographic and clinical characteristics of the PSOAS group-based trajectory modelling cohort

Characteristics	n = 561
Male, n (%)	424 (75.58)
White, n (%)	453 (80.75)
Education >high school, n (%)	467 (81.08)
Smoking history, n (%)	226 (40.29)
HLA-B27 positivity	472 (84.74)
Number of X-ray sets, median (IQR)	3 (2, 4)
Follow up years, median (IQR)	4.17 (2.25, 6.67)
Age at baseline, mean (s.d.)	41.79 (13.09)
Disease duration at baseline, median (IQR)	15.00 (7.00, 25.00)
Number of comorbidities, median (IQR)	2.00 (1.00, 3.00)
BASFI Score, median (IQR)	22.70 (9.20, 44.00)
BASDAI Score, median (IQR)	3.20 (1.60, 5.39)
First observed CRP (mg/dL), median (IQR)	0.40 (0.20, 1.00)
First observed ESR (mm/h), median (IQR)	11.00 (5.00, 21.50)
Baseline mSASSS, median (IQR)	5.00 (0.00, 26.00)
Baseline TNFi use, n (%)	236 (42.07)
Baseline NSAID use, n (%)	402 (71.66)

IQR: interquartile range.