Validity of EQ-5D utility index and minimal clinically important difference estimation among patients with chronic obstructive pulmonary disease

Table 2 HRQoL scores and effect size according to the GOLD severity

	EQ-5D utility* Mean score (SD)	EQ-VAS* Mean score (SD)	CAT* Mean score (SD)
GOLD classification of lung function and HRQoL
GOLD-1, FEV₁ ≥ 80% predicted	0.911^a (0.111)	72.97^a (11.49)	12.28^a (7.42)
GOLD-2, 50% ≤ FEV₁ < 80% predicted	0.860^a (0.117)	68.84^ab (17.18)	14.14^a (8.26)
GOLD-3, 30% ≤ FEV₁ < 50% predicted	0.792^b (0.156)	63.44^b (19.2)	19.76^b (8.62)
GOLD-4, FEV₁ < 30% predicted	0.664^c (0.169)	52.50^c (16.5)	24.85^c (7.78)
Total	0.831 (0.146)	66.52 (17.85)	16.39 (8.96)
Effect size ^d
Between GOLD-1 and GOLD-2	0.445	0.252	−0.228
Between GOLD-2 and GOLD-3	0.510	0.301	−0.670
Between GOLD-3 and GOLD-4	0.803	0.584	−0.601
Correlations for each HRQoL scores ^e
Between FEV₁% predicted	0.422	0.284	−0.371
Between GOLD grade	−0.380	−0.258	0.375

HRQoL Health-Related Quality of Life, SD standard deviation, FEV₁ forced expiratory volume in 1 s
*p < 0.001, p-value for severity group was calculated by ANOVA;
^{a; b; c;} the same superscript letters indicate non-significant difference between GOLD groups based on Duncan’s post-hoc test (p < 0.05);
^deffect size used Cohen’s d = M₁ - M₂ / S_pooled, where S_pooled = √[(S₁₂+ S₂₂) / 2];
^eSpearman’s rank correlation coefficient (p < 0.05)

ISSN: 1471-2466