Objective: Dyspnoea is a common, multifactorial source of functional impairment among patients with dcSSc. Our objective was to assess the reliability, construct validity and responsiveness to change of the Saint George's Respiratory Questionnaire (SGRQ) in patients with early dcSSc participating in a multicentre prospective study.
Methods: At enrolment and 1 year, patients completed the SGRQ (a multi-item instrument with four scales: symptoms, activity, impact and total), a visual analogue scale (VAS) for breathing and the HAQ Disability Index (HAQ-DI) and underwent 6 min walk distance and pulmonary function tests, physician and patient global health assessments and high-resolution CT (HRCT). We assessed internal consistency reliability using Cronbach's α. For validity we examined the ability of the SGRQ to differentiate the presence vs absence of interstitial lung disease (ILD) on HRCT or restrictive lung disease and evaluated the 1 year responsiveness to change using pulmonary function tests and patient- and physician-reported anchors. Correlation coefficients of 0.24-0.36 were considered moderate and >0.37 was considered large.
Results: A total of 177 patients were evaluated. Reliability was satisfactory for all SGRQ scales (0.70-0.93). All scales showed large correlations with the VAS for breathing and diffusing capacity of the lung for carbon monoxide in the overall cohort and in the subgroup with ILD. Three of the four scales in the overall cohort and the total scale in the ILD subgroup showed moderate to large correlation with the HAQ-DI and the predicted forced vital capacity (r = 0.33-0.44). Each scale discriminated between the presence and absence of ILD and restrictive lung disease (P ≤ 0.0001-0.03). At follow-up, all scales were responsive to change using different anchors.
Conclusion: The SGRQ has acceptable reliability, construct validity and responsiveness to change for use in a dcSSc population and differentiates between patients with and without ILD.
Keywords: autoinflammatory conditions; dyspnoea; patient attitude to health; patient-reported outcomes; quality of life; respiratory; scleroderma and related disorders; systemic sclerosis.
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