Convergent Validity and Minimal Clinically Important Difference of the Maugeri Foundation Respiratory Failure Questionnaire (MRF-28) and the Chronic Obstructive Pulmonary Disease-Specific Health-Related Quality of Life questionnaire (VQ11)

Figures & data

Table 1 Characteristics of Patients Solicited to Participate in the Study

	n (%) or Median (Range)
Sample size	485 (100)
Age (y)	64.0 (22.0–89.0)
Men (%)	159 (32.8)
Body mass (kg)	74.0 (35.0–150.0)
Height (m)	1.69 (1.40–1.90)
Body mass index (kg/m^2)	26.1 (14.0–56.2)
FEV1 (L)	0.93 (0.37–4.88)
FEV1 (% theoretical value)	36.0 (13.0–101.0)
FVC (L)	2.1 (0.6–5.1)
FVC (% theoretical value)	62.0 (18.0–118.0)
FEV1/FVC	49.0 (24.0–70.0)
Mild airflow limitation (FEV1 ≥ 80%)	5 (1.0)
Moderate airflow limitation (50% ≤ FEV1 < 80%)	79 (16.3)
Severe airflow limitation (30% ≤ FEV1 < 50%)	161 (33.2)
Very severe airflow limitation (FEV1 < 30%)	129 (26.6)
Refusal	1 (0.2)
Missing	110 (22.7)
LTOT	171 (35.3)
LTOT + NIV	137 (28.3)
LTOT + CPAP	14 (2.9)
NIV	24 (5.0)
CPAP	27 (5.6)
No medical equipment	112 (23.0)
Socioeconomic deprivation score	37.0 (7.0–92.0)

Abbreviations: CPAP, continuous positive airways pressure; FEV₁, forced expiratory volume in one second; FVC, forced vital capacity; LTOT, long-term oxygen therapy; NIV, non-invasive ventilation.

Table 2 Differences Between Participants and Nonparticipants

	Non-Participant Patients (n = 85)	Participant Patients (n = 400)	All Patients (n = 485)	p Value
Age (y)	68.3 (10.9)	63.5 (11.1)	64.3 (11.2)	0.0003
Men (%)	56 (65.9)	270 (67.5)	159 (32.8)	0.7729
Body mass (kg)	72.8 (22.0)	77.8 (22.3)	76.9 (22.3)	0.0638
Height (m)	1.67 (8.7)	1.69 (8.6)	1.68 (8.6)	0.0510
Body mass index (kg/m^2)	26.1 (7.5)	27.3 (7.6)	27.1 (7.6)	0.1843
FEV1 (L)	0.87 (0.40)	1.12 (0.57)	1.08 (0.56)	0.0002
FEV1 (% theoretical value)	34.3 (13.5)	40.1 (17.8)	39.2 (17.4)	0.0053
FVC (L)	1.9 (0.9)	2.2 (0.9)	2.2 (0.9)	0.0300
FVC (% theoretical value)	56.0 (18.7)	65.2 (20.0)	63.9 (20.0)	0.0120
FEV1/FVC	45.7 (11.3)	49.5 (12.8)	49.0 (12.7)	0.1039
Mild airflow limitation (FEV1 ≥ 80%)	0 (0.00)	5 (1.3)	5 (1.0)	< 0.0001
Moderate airflow limitation (50% ≤ FEV1 < 80%)	8 (9.4)	71 (17.8)	79 (16.3)
Severe airflow limitation (30% ≤ FEV1 < 50%)	22 (25.9)	139 (34.8)	161 (33.2)
Very severe airflow limitation (FEV1 < 30%)	26 (30.6)	103 (25.8)	129 (26.6)
Refusal	1 (1.8)	0 (0.0)	1 (0.2)
Missing	28 (33.0)	82 (20.5)	110 (22.7)
LTOT	39 (45.9)	132 (33.0)	171 (35.3)	0.0570
LTOT + NIV	25 (29.4)	112 (28.0)	137 (28.3)
LTOT + CPAP	4 (4.7)	10 (2.5)	14 (2.9)
NIV	3 (3.5)	21 (5.3)	24 (5.0)
CPAP	3 (3.5)	24 (6.0)	27 (5.6)
No medical equipment	11 (12.9)	101 (25.3)	112 (23.0)
Socioeconomic deprivation score	38.4 (16.9)	37.7 (18.0)	37.8 (17.8)	0.7636

Abbreviations: CPAP, continuous positive airways pressure; FEV₁, forced expiratory volume in one second; FVC, forced vital capacity; LTOT, long-term oxygen therapy; NIV, non-invasive ventilation.

Figure 1 Flow diagram of patients with chronic obstructive pulmonary disease managed by home-based pulmonary rehabilitation program.

Table 3 Effect of the Pulmonary Rehabilitation Program

	T0	T2	Mean Change	Cohen's d	p Value
10STS (s)	32.4 (15.8)	27.6 (12.3)	−4.7 (12.3)	−0.30	< 0.0001
TUG (s)	10.8 (6.7)	9.5 (6.8)	−1.3 (3.9)	−0.20	< 0.0001
6MST (strokes)	322 (159)	390 (171)	+64 (100)	0.43	< 0.0001
HAD: anxiety state (/21)	9.8 (4.5)	8.5 (4.2)	−1.4 (3.5)	−0.31	< 0.0001
HAD: depression state (/21)	8.1 (4.1)	6.2 (4.1)	−1.8 (3.7)	−0.44	< 0.0001
HAD: global score (/42)	17.9 (7.4)	14.7 (7.2)	−3.2 (6.2)	−0.43	< 0.0001
MRF-28: daily activity (/100)	52.2 (28.5)	43.1 (28.0)	−9.2 (21.6)	−0.32	< 0.0001
MRF-28: cognitive function (/100)	31.6 (36.4)	25.5 (33.4)	−6.1 (30.0)	−0.17	< 0.0001
MRF-28: invalidity (/100)	62.4 (32.3)	51.9 (34.2)	−10.4 (30.8)	−0.32	< 0.0001
MRF-28: global score (/100)	51.2 (23.1)	42.5 (22.9)	−8.8 (16.5)	−0.38	< 0.0001
VQ11: functional (/15)	10.7 (2.9)	9.5 (3.1)	−1.2 (2.5)	−0.44	< 0.0001
VQ11: psychological (/20)	11.8 (3.2)	10.6 (3.4)	−1.2 (3.0)	−0.39	< 0.0001
VQ11: social (/20)	11.0 (3.8)	9.8 (4.0)	−1.1 (3.3)	−0.30	< 0.0001
VQ11: global score (/55)	33.5 (8.9)	29.8 (9.7)	−3.5 (7.5)	−0.42	< 0.0001
VSRQ (/80)	31.1 (15.3)	39.3 (16.4)	+8.2 (13.5)	0.54	< 0.0001

Abbreviations: HAD, hospital anxiety and depression questionnaire; MRF-28, Maugeri Foundation respiratory failure questionnaire; TUG, timed up-and-go test; VQ11, COPD specific HRQoL questionnaire; VSRQ, visual simplified respiratory questionnaire; 6MST, 6 min stepper test; 10STS, 10 times sit-to-stand test.

Table 4 Correlations Between VSRQ and the Other Questionnaires at T₀ and T₂ and the Deltas (T_0-T₂)

		MRF-28: Global Score	VQ11: Global Score
T0	Correlation coefficient	−0.685	−0.691
	p value	< 0.0001	< 0.0001
T2	Correlation coefficient	−0.686	−0.753
	p value	< 0.0001	< 0.0001
Delta	Correlation coefficient	−0.372	−0.423
	p value	< 0.0001	< 0.0001

Abbreviations: MRF-28, Maugeri Foundation respiratory failure questionnaire; T₀, baseline (ie, before pulmonary rehabilitation); T₂, after pulmonary rehabilitation; VQ11, COPD specific HRQoL questionnaire; VSRQ, visual simplified respiratory questionnaire.

Table 5 Determination of Minimal Clinically Important Difference Using Two Statistical Methods

Method	MRF-28: Global Score	VQ11: Global Score	VSRQ: Global Score
Anchor based
ROC curve derived (Youden)	28	5	5
ROC curve derived (“Minimax”: minimizes the most frequent error)	24	1	2
Distribution based
Half Standard deviation	5.77	2.22	3.83
Small Cohen’s effect size (0.2)	4.62	1.77	3.06
MCID proposed	−5.2	−2.0	+3.4

Abbreviations: MRF-28, Maugeri Foundation respiratory failure questionnaire; ROC, receiver operating characteristics; VQ11, COPD specific HRQoL questionnaire; VSRQ, visual simplified respiratory questionnaire.