Table 4.

Exploration of factors contributing to the SGRQ-I in patients with IPF using stepwise multivariate analyses

Variables	Symptoms	Activity	Impacts	Total
%FVC
%Dlco
6MWD
Minimum SpO2 during 6MWT	0.24	0.15	0.21	0.21
PaO2 on room air			0.11
mMRC	0.15	0.50	0.23	0.34
HADS Anxiety		0.21
HADS Depression		0.14	0.28	0.23
PSQI
Cumulative R2	0.60	0.79	0.83	0.78

Data are presented as the coefficients of determination (R²).

R² is shown when p < 0.05.

Abbreviations: SGRQ-I, idiopathic pulmonary fibrosis-specific version of the St. George’s Respiratory Questionnaire; IPF, idiopathic pulmonary fibrosis; %FVC, percentage of the predicted forced vital capacity; %DLCO, percentage of the predicted diffusing capacity of the lung for carbon monoxide; 6MWD, six-minute walk distance; SpO2, oxygen saturation measured by pulse oximetry; 6MWT, six-minute walk test; PaO₂ partial pressure of arterial oxygen; mMRC, modified Medical Research Council; HADS, Hospital Anxiety and Depression Scale; PSQI, Pittsburgh Sleep Quality Index.