Validity of the Saint George's respiratory questionnaire in the evaluation of the health-related quality of the life in patients with interstitial lung disease secondary to systemic sclerosis

Objectives. Interstitial lung disease (ILD) profoundly affects the health-related quality of life (HRQoL) in patients with systemic sclerosis (SSc). We tested the validity of the Saint George's Respiratory Questionnaire (SGRQ), a lung-specific HRQoL-evaluation tool, in a population of SSc patients with ILD. Methods. Twenty-eight consecutive SSc patients with a restrictive pulmonary involvement, defined as a forced vital capacity <80% of the predicted, with no pulmonary hypertension were considered. All the patients filled in the Medical Research Council (MRC) scale for perceived breathlessness, the SGRQ and the Disability Index of the Health Assessment Questionnaire (HAQ DI), and underwent evaluation with complete pulmonary function testing (PFT), 6-minute walk distance (6MWD) and high-resolution computed tomography (HRCT). Results. The SGRQ 'activity' scores inversely correlated with the 6MWD (r = -0.86, P < 0.001) and forced vital capacity percentage of predicted values (r = -0.47) and directly correlated with HRCT (r = 0.41, P < 0.05), MRC (ρ = 0.64, P < 0.001) or HAQ DI scores (r = 0.62, P < 0.001), independently of disease duration or subset. On the contrary, HAQ DI scores were influenced by those variables and corrected correlations with 6MWD (r = 0.56, P < 0.001) or HRCT scores (r = 0.36, P = NS) were less strong than those observed with the SGRQ. Conclusions. The SGRQ, although not specifically designed for scleroderma, is a valid respiratory-specific questionnaire for the evaluation of HRQoL in patients with SSc-related ILD. The SGRQ performs better in relation to exercise capacity and lung imaging than other non-respiratory-specific questionnaires widely used in scleroderma studies. Further studies are needed to address its ability to assess changes over time or in response to therapy.