Use of Spirometry and Respiratory Drugs in Manitobans Over 35 Years of Age with Obstructive Lung Diseases

Abstract

Previous data indicated that spirometry was underused in people with obstructive disease, especially those with chronic obstructive pulmonary disease (COPD). To examine the use of respiratory drugs in patients with COPD and asthma, and to relate drug use to spirometry. Manitoba Health maintains a database of physician services remunerated by fees that includes spirometry. The database contains the diagnosis and patient identifiers, as well as sex, date of birth and residential postal code. Similar identifiers are used in the provincial pharmacare program that records prescriptions dispensed at retail pharmacies. These databases were examined for the time period between 1996 to 2000, and people over 35 years of age diagnosed with asthma, COPD or both were identified. The frequency of spirometry in these patients and their use of respiratory drugs was determined. Spirometry and drug prescription frequencies increased with the number of physician visits (including those for bronchitis), but their patterns differed. Patients with asthma or asthma plus COPD had considerably higher rates of drug prescription and slightly higher spirometry rates than did those with COPD. Patients with asthma and asthma plus COPD who underwent spirometry were slightly more likely to receive drugs than those who did not undergo spirometry; this trend was more striking in patients with COPD. However, approximately 30% of patients with COPD who had five physician visits and who underwent spirometry did not receive drugs; this was true for approximately 10% of similar patients with asthma. Patients with asthma generally received beta-agonists and inhaled steroids; these agents were less commonly given to patients with COPD, who instead were given anticholinergics much more often than were asthmatics. Patients who were diagnosed with asthma plus COPD had beta-agonist and inhaled corticosteroid prescription rates similar to asthmatics, and anticholinergic prescription rates similar to patients with COPD. Theophylline and antileukotriene drugs were used less often than were inhaled agents. In patients with asthma, drugs were frequently discontinued, and during drug use, prescription refills were consistent with an intake of 30.9% of the prescribed doses. In patients with COPD, discontinuing drugs early was uncommon, and refills were consistent with the use of 54% of the prescribed amounts. The same was true of patients with both COPD and asthma. Drug prescription was considerably more common in patients labelled with asthma or COPD plus asthma than in patients with COPD. Spirometry was also less common in patients with COPD but had a distinct influence on the frequency of drug prescription. Patterns of drug prescription were predictable, and patterns of drug use indicated poor compliance, in agreement with other data. The results suggest that COPD symptoms may be discounted and patients systematically undertreated or the diagnosis could frequently be applied to people with trivial disease or both.