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The heterogeneity of chronic obstructive pulmonary disease
  1. Academic Respiratory Medicine
  2. St Bartholomew's and Royal London School of Medicine and Dentistry
  3. St Bartholomew's Hospital
  4. London EC1A 7BE
  5. UK
  6. email:

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    Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality in adults and has important health economic consequences. Despite being such an important cause of health impairment,1 the diagnosis of COPD is often made relatively late in the natural history of the disorder when there is already an appreciable fall in the forced expiratory volume in one second (FEV1) and symptomatic deterioration, as the early stages of the disease are relatively asymptomatic. COPD is formally defined by spirometric criteria according to the British Thoracic Society (BTS) guidelines on the management of COPD as a chronic slowly progressive disorder characterised by largely fixed airways obstruction (FEV1 <80% predicted and FEV1/FVC ratio of <70% predicted).2 However, we now know that COPD is a largely heterogeneous condition, consisting of a number of pathological processes whose effects are modified by varied host susceptibility.3 Some patients present with daily symptoms of cough and sputum production, suggestive predominantly of chronic airway inflammatory processes, that can make the differential diagnosis from bronchiectasis difficult in clinical practice. Others complain predominantly of dyspnoea caused by the hyperinflation associated with the disease and may have a different natural history from those producing sputum. Early studies showed little association between the hypersecretory and obstructive forms of COPD,4 but other studies have shown positive relationships between chronic mucus hypersecretion and decline in FEV1.5 Knowledge of the natural history of these different processes and methods of diagnosis of COPD is still generally poor, making early detection of COPD patients problematical and identification of those who may be most susceptible to exacerbation and hospital admission particularly difficult.

    Most patients who present with COPD in …

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