Diagnosing COPD

Diagnosing COPD It is widely recognized that many people with chronic obstructive pulmonary disease (COPD) are undiagnosed, including some with significant airflow obstruction. The best available data suggest that the prevalence of physiologically defined COPD in adults aged 40 years is 9%–10% (Halbert et al 2006). In their study of randomly selected individuals aged 60 to 74 years from a UK general practice register, Dickinson and colleagues (1999) found that there were 2.69 " true " cases of COPD for each diagnosed case, with an overall prevalence of 6.2% with undiagnosed COPD. A similar study of a random sample of the general population aged over 64 years in Finland found 1.99 and 1.62 true cases of COPD for each diagnosed case in men and women, respectively (Isoha et al 1994). Other studies have compared the prevalence of respiratory symptoms with patient-reported diagnoses and found a ratio of true COPD cases to self-reported diagnoses ranging from approximately 1.5 to 4 (Littlejohns et al 1989; Lundback et al 1991; Viegi et al 1991; Lai et al 1995). Most recently a study in Manchester by Frank and colleagues (2006) found that nearly two thirds of patients with spirometrically confirmed COPD had no prior diagnosis of COPD and nearly half of these had severe airflow obstruction. Some of these patients have no diagnosis of airways disease at all and others are misdiagnosed as asthmatics. It has been suggested that COPD and asthma are simply different phenotypes of a common obstructive disease; the so called Dutch Hypothesis (Bleecker 2004). This has led to the suggestion that differentiation is unnecessary, particularly as treatment uses similar drugs (Kraft 2006). However, most evidence suggests that asthma and COPD have a different etiology and pathophysiology, and require different management (Barnes 2006). Although similar drugs are used in both diseases they are used in different sequences and with different doses. For example, low dose inhaled steroids are essential in patients with asthma whose symptoms are persistent, whilst in COPD inhaled steroids are principally recommended in patients with an forced expiratory volume in one second (FEV 1) of <50% and experiencing frequent exacerbations. The evidence for their efficacy is based on use at a high dose (Fabbri and Hurd 2003; NICE 2004). Perhaps the most important reason for distinguishing the two conditions is the fact that they have very different prognoses. Most asthmatics maintain normal or near normal lung function and …