Table 4

Estimates for clinically relevant thresholds for improvement and deterioration on the CAT

CAT	T3–T0		T6–T0		T12–T0		Weighted threshold
Change	Improvement	Deterioration	Improvement	Deterioration	Improvement	Deterioration	Improvement	Deterioration
Minimal change
Anchor-based PR (n)	107	36	96	42	88	43	291	121
Anchor-based PR	−2.74	2.71	−2.73	3.21	−2.80	4.21	−2.75	3.42
Anchor-based RCP (n)	12	27	14	36	18	46	32	82
Anchor-based RCP	–	–	−2.86	1.97	−3.78	1.63	−3.38	1.78
Distribution-based PR (n)	227	127	184	135	180	129	591	391
Distribution-based PR	−2.29	2.10	−2.17	2.05	−2.33	2.11	−2.26	2.09
Distribution-based RCP (n)	102	83	81	91	79	86	262	260
Distribution-based RCP	−1.67	1.83	−1.53	1.44	−1.58	1.30	−1.60	1.52
Moderate change
Anchor-based PR (n)	51	9	45	7	37	10	133	17
Anchor-based PR	−5.02	–	−3.29	8.14	−4.27	6.30	−4.23	7.06
Anchor-based RCP (n)	5	8	12	9	5	9	–	9
Anchor-based RCP	–	–	–	–	–	3.89	–	3.89
Large change
Anchor-based PR (n)	16	3	12	2	14	3	42	–
Anchor-based PR	−4.19	–	−7.00	–	−6.07	–	−5.62	–
Anchor-based RCP (n)	4	3	0	2	9	4	13	4
Anchor-based RCP	−6.00	–	–	–	−4.22	5.75	−4.77	5.75
No change
Anchor-based PR (n)	133		115		114		362
Anchor-based PR	0.03		−0.01		−0.33		−0.10
Anchor-based RCP (n)	141		113		83		337
Anchor-based RCP	−0.16		−0.54		−0.47		−0.36

Data reported as clinically relevant threshold or n. Negative change represents improvement for all health status instruments. Paired t-tests were applied with significance level at p<0.05. Non-significant results were excluded, except for the ‘No change’ group.
CAT, COPD Assessment Test; n, number of patients; PR, pulmonary rehabilitation; RCP, routine clinical practice; T0, baseline measurement; T3, 3-month follow-up; T6, 6-month follow-up; T12, 12-month follow-up.