Peak expiratory flow as a surrogate for health related quality of life in chronic obstructive pulmonary disease: a preliminary cross sectional study.

BACKGROUND Health Related Quality of Life (HRQL) measures can capture the non-respiratory effects of Chronic Obstructive Pulmonary Disease (COPD). However the relationship with Peak Expiratory Flow (PEF) is not well understood. AIM To determine the relationship of PEF and quality of life measurements in patients with COPD. SETTINGS AND DESIGN A cross section of consecutive patients in a university clinic. METHODS Stable patients with COPD defined by the Global Initiative on chronic Obstructive Lung Disease (GOLD) criteria, were recruited into the study. Spirometry was done using American Thoracic Society's standards and reference equations from African American norms of the US population. Quality of life was measured with the St George's Respiratory Questionnaire (SGRQ). RESULTS Out of 50 patients recruited for the study, 48 provided complete data with acceptable spirometry and PEF data. The mean (SD) age and body mass index was 68.4 (8.9) years and 21.4 (4.6) kg/m(2) respectively and 96% of the patients were in moderate-severe stages of COPD using the GOLD criteria. Percent predicted PEF correlated with percent predicted FEV1; r= 0.559 p<0.001 and also showed a significant, though moderate correlation between PEF readings and SGRQ scores especially in the activity (r= -0.455 p< 0.01) and total scores (r=-0.415 p<0.01) for pre bronchodilator (BD) percent predicted PEF. In regression analysis, PEF was associated with SGRQ (-0.11 95% CI -0.19, -0.03) after adjusting for age, sex, height, smoking and disease severity. CONCLUSIONS PEF correlates with SGRQ scores and may be a useful surrogate for HRQL in patients with COPD.