Feasibility of spirometry and reversibility testing for the identificationof patients with chronic obstructive pulmonary disease on asthma registersin general practice

There is renewed interest in the diagnosis of chronic obstructive pulmonary disease (COPD) within primary care. Primary care physicians have difficult y distinguishing asthma from COPD. We tested the feasibility of using spiro metry and if appropriate, reversibility testing, to identify patients with COPD on asthma registers in primary care. We carried out a cross-sectional study in three inner-city group practices in east London. Three hundred and twenty-eight patients aged 50 years and o ver on practice asthma registers were invited to attend for spirometry and. if appropriate, a trial of oral corticosteroids. The main outcome measures were: feasibility of carrying out spirometry; lung function; severity of C OPD; prior diagnosis of COPD; response to a corticosteroid trial; quality o f life. One hundred and sixty-eight of 328 (51%) patients attended for spirometry. According to British Thoracic Society criteria, 58 (34%) patients had norma l spirometry at the time of assessment; 40 (24%) had active asthma and 57 ( 34%) had COPD. Thirteen patients (8%) were unable to perform spirometry. Of 57 patients with COPD 30 (53%) had mild, 15 (26%) had moderate and 12 (21% ) had severe disease. Twenty-three of 57 (40%) patients with COPD on spirom etry had this diagnosis recorded prior to the study. New diagnoses of COPD were more likely in those with mild or moderate disease (P < 0.05). Twenty- three of 57 (40%) patients with COPD completed a corticosteroid trial: one showed significant reversibility of lung function. Spirometry was feasible and helped identify patients with COPD on asthma re gisters in these inner-city practices. Patients aged 50 years and over on a sthma registers had a wide spectrum of lung function with considerable diag nostic misclassification. Some patients with normal lung function when test ed may have had well controlled asthma. New diagnoses of COPD were mainly i n those with mild or moderate disease. (C) 1999 HARCOURT PUBLISHERS LTD.