TABLE 3

Associations of changes in lung function or symptoms with computed tomography-measured residual volume/total lung capacity (RV_CT/TLC_CT) strata

Outcome parameters	RV_CT/TLC_CT strata	Differences in estimates	95% CI	p-value
FEV₁ mL
	High	−20.2	−66.8 to 26.3
	Intermediate	−23.7	−65.2 to 18.5	0.525
	Low	Ref.
FVC mL
	High	29.3	−35.1 to 94.5
	Intermediate	4.6	−53.9 to 62.7	0.623
	Low	Ref.
FEV₁/FVC %
	High	−1.43	−2.31 to −0.57
	Intermediate	−0.91	−1.69 to −0.12	0.005
	Low	Ref.
FEF_25–75% mL
	High	−86.2	−185.5 to 12.2
	Intermediate	−77.4	−165.7 to 11.4	0.164
	Low	Ref.
FEF_75% mL
	High	−53.2	−107.8 to 1.0
	Intermediate	−42.7	−91.7 to 6.7	0.127
	Low	Ref.
Expiratory time s
	High	0.13	−0.55 to 0.81
	Intermediate	0.60	−0.02 to 1.21	0.120
	Low	Ref.
6-MWD m
	High	−15.4	−32.2 to 1.2
	Intermediate	−19.4	−34.6 to −4.2	0.041
	Low	Ref.
BODE index
	High	0.20	0.02 to 0.39
	Intermediate	0.16	−0.01 to 0.32	0.074
	Low	Ref.
CAT score
	High	−0.007	−1.208 to 1.202
	Intermediate	−0.019	−1.133 to 1.089	0.999
	Low	Ref.
mMRC
	High	0.175	0.025 to 0.327
	Intermediate	0.172	0.033 to 0.311	0.031
	Low	Ref.
SGRQ total score
	High	1.68	−0.72 to 4.12
	Intermediate	0.18	−2.05 to 2.45	0.312
	Low	Ref.
SGRQ symptom score
	High	1.99	−1.84 to 6.02
	Intermediate	1.23	−2.33 to 4.88	0.604
	Low	Ref.
SGRQ activity score
	High	3.28	0.10 to 6.50
	Intermediate	1.49	−1.51 to 4.45	0.138
	Low	Ref.
SGRQ impact score
	High	0.99	−1.31 to 3.32
	Intermediate	0.34	−1.77 to 2.47	0.692
	Low	Ref.
SF12 physical component
	High	−0.74	−1.72 to 0.20
	Intermediate	−0.67	−1.56 to 0.19	0.231
	Low	Ref.
SF12 physical functioning
	High	−1.39	−2.58 to −0.26
	Intermediate	−1.33	−2.39 to −0.30	0.022
	Low	Ref.

Association of changes in lung function and symptoms outcomes with computed tomography-measured residual volume/total lung capcity (RV_CT/TLC_CT) strata were estimated using mixed-effect linear regression models with adjustment for age, sex, height, weight, smoking status, smoking burden, and random effects from length of follow-up time and study site. FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; FEF_25–75%: forced expiratory flow at 25–75% of FVC; FEF_75%: forced expiratory flow at 75% of FVC; 6-MWD: 6-minute walk distance test; BODE: body–mass index, airflow obstruction, dyspnoea and exercise capacity; CAT: COPD assessment test; mMRC: modified Medical Research Council dyspnoea scale; SGRQ: Saint George's Respiratory Questionnaire; SF12: Short Form 12-Item survey; Ref: reference value. p-values are from mixed-effect linear regression modelling with a nested random subject and site effect. Significant associations are shown in bold.