The St George's Respiratory Questionnaire is not useful in the assessment of early chronic obstructive pulmonary disease
The St George's Respiratory Questionnaire (SGRQ) is a widely used tool for the assessment of respiratory disease. It is a self-completed questionnaire, output is in the form of three scores (symptoms, activity and impacts) and a mean total (Jones,PW et al. Am Rev Resp Dis 1992). As part of an on-going study into early chronic obstructive pulmonary disease (COPD) we have looked at the usefulness of the SGRQ in the assessment of smokers who have not presented to physicians with COPD. Asymptomatic smokers were selected from the database of a large urban general practice. 118 were invited by post to attend a local chest clinic. There was a 34.7% response rate. All subjects underwent lung function (FEV1, FVC, Residual Volume [RV]), Transfer Factor [KCO]) and completed the SGRQ. 34 subjects have been screened. The SGRQ scores were correlated with lung function for those with and without COPD. 15 subjects were female. 11 subjects had COPD (FEV1/FVC ratio <70%) with negative steroid and beta agonist trials, mean FEV1/FVC 57.8 (95%CI 51.6-64.0). Non-COPD subjects (n=23) had mean FEV1/FVC ratio 78.3 (95%CI 76.2-80.3). The two groups were matched for smoking history. There was no significant difference between KCO and RV although there was a tendency for the KCO and RV to be higher in the non-COPD group (p=0.064 and 0.11 respectively). The SGRQ scores for both groups were significantly different from the population normal ranges (total score 24.8 95% CI 14.37-35.22 for COPD and 15.16 95% CI 8.26-22.1 vs. 6 95% CI 5.0-7.0). There was correlation for male smokers between all SGRQ scores and FEV1/FVC (symptoms r2= 0.24 p<0.05, activity r2= 0.39 p<0.01, impacts r2= 0.64 p<0.001, total score r2= 0.47 p<0.005) and impact score and RV (r2= 0.39 p<0.01). No correlations were found for females or those with and without COPD. The use of the SGRQ is limited in asymptomatic smokers with early COPD and cannot be used as a method to differentiate between those with and without COPD. It was found to be of use in male smokers only. The SGRQ should be interpreted with caution even in asymptomatic smokers as they score significantly higher with this measure than normal subjects.