Validity and Reliability of the St George's Respiratory Questionnaire in Adults With Cystic Fibrosis

Objective To study self-perceived quality of life in adults with cystic fibrosis (CF), and to assess the validity of the St George's Respiratory Questionnaire (SGRQ) for use in these patients. Patients and methods We studied 37 adults with CF who were in stable condition as indicated by their respiratory and nutritional status. Disease severity was assessed by spirometry used in conjunction with a modified National Institutes of Health (NIH) scoring system and the Bhalla scale. Nutritional status was evaluated by measuring height and weight, calculating body mass index, analyzing bioelectric impedance, and performing various laboratory tests. The patients' quality of life was assessed using the SGRQ. Results SGRQ scores were higher (indicating poorer quality of life) among patients with CF than in the general population or among patients with chronic obstructive pulmonary disease. Internal consistency coefficients indicated the SGRQ had good reliability (Cronbach's alpha, 0.864). Women with CF tended to score higher than men, although this difference was not statistically significantly. A statistically significant relationship was observed between SGRQ score and severity of pulmonary impairment (the more severe the impairment, the worse the patient's quality of life). Statistically significant positive relationships were found between SGRQ domains and age, body mass index, and body fat percentage. Significant negative relationships were found between these domains and the modified NIH score, the Bhalla score, forced expiratory volume in 1 second (expressed as a percentage of predicted), and somatomedin C and zinc levels. Conclusions Self-perceived quality of life is worse among adults with CF than in the general population or among patients with chronic obstructive pulmonary disease. The SGRQ is a valid instrument for analyzing health-related quality of life in adults with CF as it discriminates very well between different degrees of severity of pulmonary impairment and has acceptable internal consistency.