Comparative study of two quality of life questionnaires in patients with COPD

Objective: To compare two quality of life questionnaires-the Saint George's Respiratory Questionnaire (SGRQ) and the Medical Outcomes Study 36-item Short-Form Health Survey (SF-36)-in patients with COPD, focusing on the discriminative properties of the questionnaires and correlating their domains with the following variables: Modified Medical Research Council Dyspnea Scale Score; Beck Depression Inventory score; visual analog scale general health perception; Mini-Mental State Examination score; and a COPD clinical score developed specifically for the study. Methods: We interviewed 30 COPD patients between May and September of 2006. For the SF-36 and SGRQ, scores (total and domain) were compared and correlated. Results: With the exception of the pain domain, all of the SF-36 domains correlated significantly with the SGRQ total score (r = -0.5 to -0.69; p < 0.01). Of the SGQR domains, only the symptoms domain correlated significantly with all of the variables studied (p < 0.05). Conclusions: The majority of the expected correlations between the SGRQ and the SF-36 were observed, as were those expected between the two questionnaires and the other variables studied. The SGRQ, notably the symptoms domain, presented better discriminative properties than did the generic SF-36 questionnaire. The SF-36 is not an appropriate instrument for determining the affective state of COPD patients.