Cross-sectional and longitudinal construct validity of the Saint George's Respiratory Questionnaire in patients with IPF

Background and objective: This study was performed to confirm the cross‐sectional and longitudinal construct validity of the Saint George's Respiratory Questionnaire (SGRQ) for the measurement of health‐related quality of life (HRQoL) in patients with IPF. Methods: Sixty‐eight patients with IPF responded to the SGRQ and pulmonary function tests (PFT), dyspnoea testing, arterial blood gas analysis, 6‐min walk tests (6MWT) and high‐resolution computed tomography were performed in a baseline study. A follow‐up study was performed on 45 of these patients. Results: In the baseline study HRQoL as measured by the SGRQ was substantially impaired in IPF patients, especially in symptoms and activity domains. A significant decline in HRQoL was observed in the activity domain during follow up. TLC and changes in TLC showed the most significant inverse correlations with each SGRQ domain ( r < −0.3, P < 0.05). In a stepwise multiple regression analysis, TLC contributed most significantly to each SGRQ component baseline score. Similar results were also observed during follow up. There was a significant correlation between total CT scores and each component of the SGRQ ( r > 0.3, P ≤ 0.001). Changes in ground‐glass opacity on CT (CT‐alv) were also correlated with changes in each SGRQ domain ( r > 0.3, P ≤ 0.001). Stepwise multiple regression analysis showed that interstitial opacity on CT (CT‐fib) contributed to variation in the baseline activity score, and that changes in CT‐alv independently contributed to overall changes in the SGRQ domains during follow up. The dyspnoea score, and changes in the dyspnoea score, correlated significantly with the SGRQ sores, with the exception of the symptoms score, in both the baseline and follow‐up studies. Conclusions: HRQoL as assessed by the SGRQ showed good cross‐sectional and longitudinal construct validity in patients with IPF. However, additional studies are required to analyse the reliability and responsiveness so that the SGRQ can be used in patients with IPF.