Longitudinal validity and prognostic significance of the St George's Respiratory Questionnaire in Mycobacterium avium complex pulmonary disease

Abstract

BackgroundAlthough previous cross-sectional studies showed the feasibility and clinical association of the St. George's Respiratory Questionnaire (SGRQ) in Mycobacterium avium complex pulmonary disease (MAC-PD), its longitudinal validity is poorly understood. We aimed to determine the longitudinal validity and prognostic significance of SGRQ. MethodsIn this prospective observational study conducted between May 2012 and August 2018, we evaluated 269 enrolled patients with MAC-PD and examined associations between baseline SGRQ total scores and mortality or clinical variables (anchors), including serum C-reactive protein levels and pulmonary function test results. ResultsAge- and sex-matched SGRQ scores indicated significantly greater impairment in patients with MAC-PD than in the general population (P < 0.001). On multivariable Cox proportional hazards regression analysis, the SGRQ total score ≥25 was an independent risk factor for mortality (adjusted hazard ratio, 5.90; 95% confidence interval, 1.65–37.7) as well as age, body mass index, and forced vital capacity (FVC). Mixed-effect model results showed a significant association between SGRQ symptom/total scores and forced expiratory volume in 1 s (FEV1), FVC, and diffusing carbon monoxide capacity. Older age, a positive smear, non-nodular/bronchiectatic form, and cavity regions were associated with SGRQ total score deterioration. Patients with a greater decline from baseline FEV1 (% predicted) exhibited significantly worse impairment in the SGRQ total score (mean ± SE, 4.69 ± 10.9 points, P = 0.001). ConclusionsSGRQ showed longitudinal validity in assessing disease severity and was sensitive to changes in patients with MAC-PD, especially changes in %FEV1. The SGRQ total score may be an important prognostic factor.