Table 3

Univariable and multivariable generalised estimating equation analysis (ASDAS model)

	Univariable (n=335)			Multivariable Low education (n=153)			Multivariable High education (n=123)
Variable	B	95% CI	p	B	95% CI	p	B	95% CI	p
Age (years)	0.26	−0.04 to 0.55	0.09	0.02	−0.40 to 0.45	0.92	0.17	−0.26 to 0.60	0.43
Male gender	−6.78	−13.58 to 0.02	0.05	−0.93	−10.39 to 8.53	0.85	−2.68	−12.41 to 7.06	0.59
High education	−7.91	−14.70 to −1.12	0.02	N/A†			N/A†
ASDAS	12.46	10.45 to 14.48	<0.01	13.08	11.05 to 15.11	<0.01	10.51	7.10 to 13.91	<0.01
BASDAI (0–10)	7.73	6.87 to 8.58	<0.01	‡			‡
Patient global assessment (0–10)	5.55	4.89 to 6.21	<0.01	‡			‡
NSAID, current	−0.30	−5.11 to 4.52	0.90	§			§
csDMARD, current	4.76	−1.20 to 10.72	0.12	§			§
bDMARD/tsDMARD, current	−2.47	−7.19 to 2.24	0.30	§			§
Time, post-onset versus pre-pandemic*	5.32	1.82 to 8.82	<0.01	9.57	5.63 to 13.51	<0.01	1.49	−5.39 to 8.36	0.67

Variables that were possibly associated with the outcome in univariable analysis (p<0.10) were considered for multivariable analysis. Next, these were retained in multivariable models if they were significantly associated with the outcome (p<0.05). Age, gender and the primary variable of interest (time, post-onset vs pre-pandemic) were always included.
*Binary time-varying variable, indicating whether an assessment took place after onset of pandemic versus pre-pandemic (primary variable of interest). As patients were followed up over time, they could have both pre-pandemic assessments (before March 2020, coded 0) and post-onset assessments (after March 2020, coded 1).
†Used for stratification.
‡Due to collinearity, ASDAS, BASDAI and Patient global assessment were not included in the same model.
§Not associated with outcome in univariable analysis.
ASDAS, Ankylosing Spondylitis Disease Activity Score; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; bDMARD, biological disease-modifying antirheumatic drug; csDMARD, conventional synthetic disease-modifying antirheumatic drug; N/A, not applicable; NSAID, non-steroidal anti-inflammatory drug; tsDMARD, targeted synthetic disease-modifying antirheumatic drug.