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Diagnosing COPD

Chronic obstructive pulmonary disease is characterised by airflow obstruction that is usually progressive, not fully reversible and does not change markedly over several months. The diagnosis is suspected on the basis of symptoms, (particularly breathlessness or cough) and signs and supported by spirometry¹. There are separate articles covering Management of Stable COPD in Primary Care and Exacerbations of Chronic Obstructive Pulmonary Disease.

Presentation In the early stages COPD may produce minimal or no symptoms.

• Opportunistic case finding should be based on the presence of risk factors (age and smoking) and symptoms. The diagnosis should be confirmed using spirometry¹.
• As the disease progresses the symptoms in individual patients vary.
• Individual symptoms in isolation are not useful in excluding or making the diagnosis of COPD.

Symptoms

• A diagnosis of COPD should be considered in patients over the age of 35 who have a risk factor (generally smoking) and who present with one or more of the following symptoms¹:
  • Exertional breathlessness, chronic cough, regular sputum production, frequent winter 'bronchitis', wheeze
• Patients in whom a diagnosis of COPD is considered should also be asked about the presence of the following factors:
  • Weight loss, effort intolerance, waking at night, ankle swelling, fatigue
• The MRC dyspnoea scale should be used to grade the level of breathlessness¹:
  1. Not troubled by breathlessness except on strenuous exercise
  2. Short of breath when hurrying or walking up a slight hill
  3. Walks slower than contemporaries on level ground because of breathlessness or has to stop for breath when walking at own pace
  4. Stops for breath after walking about 100m or after a few minutes on level ground
  5. Too breathless to leave the house, or breathless when dressing or undressing

Signs Individual clinical signs are not helpful in making a diagnosis of COPD and in some patients there may be no abnormal physical signs. The following signs may be present¹:

• Cachexia
• Hyperinflated chest, purse lip breathing, use of accessory muscles, paradoxical movement of lower ribs, reduced crico-sternal distance
• Wheeze or quiet breath sounds
• Reduced cardiac dullness on percussion
• Peripheral oedema
• Cyanosis
• Raised JVP

Differential Diagnosis

• Asthma
• Bronchiectasis
• Congestive cardiac failure
• Carcinoma of the bronchus
• Obliterative bronchiolitis
• Bronchopulmonary dysplasia

Investigations

• Spirometry should be performed in patients who are over 35, current or ex-smokers, and have a chronic cough.
• Spirometry should be considered in patients with chronic bronchitis. A significant proportion of these will go on to develop airflow limitation.

Peak expiratory flow rate

• Measurement may significantly underestimate the severity of the airflow limitation.
• A normal peak expiratory flow rate does not exclude significant airflow obstruction.

Spirometry

• Spirometry is the only accurate method of measuring the airflow obstruction in patients with COPD. Spirometry should be performed at the time of diagnosis and to reconsider the diagnosis, if patients show an exceptionally good response to treatment.
• The recommended ERS 1993 reference values may lead to under-diagnosis in the elderly and are not applicable in black and Asian populations.
• A diagnosis of airflow obstruction can be made if the FEV1/FVC less than 0.7 (i.e. 70%) and FEV1 less than 80% predicted.
• Values for the forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) must be compared with the predicted normal values which depend on the individual's age, height and sex.
• Spirometry is a poor predictor of disability and quality of life in COPD but helps in predicting prognosis and contributes to the assessment of the severity of COPD. Spirometry alone cannot separate asthma from COPD.
• Reversibility testing
  • In most cases the diagnosis of COPD is suggested by the combination of the clinical history, signs and baseline spirometry. Reversibility testing does not add any additional information.
  • There is now evidence that the clinical response to bronchodilators or inhaled corticosteroids cannot be predicted by response to a reversibility test. If patients report a marked improvement in symptoms in response to inhaled therapy, the diagnosis of COPD should be reconsidered.
  • Longitudinal observation of patients (whether using spirometry, peak flow or symptoms) should also be used to help differentiate COPD from asthma. To help resolve cases where diagnostic doubt remains, or both COPD and asthma are present, the following findings should be used to help identify asthma:
    • Large (over 400ml) response to bronchodilators
    • Large (over 400ml) response to 30mg oral prednisolone daily for 2 weeks
    • Serial peak flow measurements showing 20% or greater diurnal or day-to-day variability.
• Clinically significant COPD is not present if the FEV1 and FEV1/FVC ratio return to normal with drug therapy
• Changes in the flow volume loop may give additional information about mild airflow obstruction.
• Measurement of the slow vital capacity may allow the assessment of airflow obstruction in patients who are unable to perform a forced manoeuvre to full exhalation.

Further investigations If diagnostic uncertainty remains, referral for more detailed investigations, including imaging and, measurement of TLCO, should be considered.

• At the time of their initial diagnostic evaluation, in addition to spirometry all patients should have:
  • Chest x-ray to exclude other pathologies
  • Full blood count to identify anaemia or polycythaemia
  • Body mass index calculated.
• Additional investigations should be performed to aid management in some circumstances:
  • Serial domiciliary peak flow measurements: to exclude asthma if diagnostic doubt remains
  • Alpha-1 antitrypsin: if early onset, minimal smoking history or family history
  • Transfer factor for carbon monoxide (TLCO): to investigate symptoms that seem disproportionate to the spirometric impairment
  • CT scan of the thorax: to investigate symptoms that seem disproportionate to the spirometric impairment, investigate abnormalities seen on a chest x-ray and assess suitability for surgery
  • ECG: to assess cardiac status if features of cor pulmonale
  • Echocardiogram: to assess cardiac status if features of cor pulmonale
  • Pulse oximetry: To assess need for oxygen therapy. If cyanosis, or cor pulmonale present, or if FEV1 less than 50% predicted
  • Sputum culture: to identify organisms if sputum is persistently present and purulent

Assessment of severity

• Spirometry can be used to assess the severity of airflow obstruction and can be used to guide therapy and predict prognosis. However using spirometry alone may underestimate the impact of the disease in some patients and overestimate it in others.
• The severity of airflow obstruction should be assessed according to the reduction in FEV1:
  • Mild airflow obstruction 50-80% predicted
  • Moderate airflow obstruction 30-49% predicted
  • Severe airflow obstruction less than 30% predicted
• Mild airflow obstruction can be associated with significant disability in patients with COPD.
• A true assessment of severity should include assessment of the degree of airflow obstruction and disability, the frequency of exacerbations and the following prognostic factors:
  • Health status, breathlessness (MRC scale), BMI, exercise capacity
  • FEV1, TLCO, partial pressure of oxygen in arterial blood (PaO2)
  • Cor pulmonale

Prevention

• Smoking cessation is by far the most important factor in preventing COPD and slowing the rate of decline in lung function. However avoidance of other causes of chronic lung disease, particularly occupational hazards, is also very important.

Referral Reasons for referral to secondary care include¹:

• Diagnostic uncertainty, suspected severe COPD, rapid decline in FEV1, symptoms disproportionate to lung function deficit, patient requests a second opinion
• Dysfunctional breathing, onset of cor pulmonale, bullous lung disease
• Frequent infections: to exclude bronchiectasis
• Assessment for oxygen therapy, long-term nebuliser therapy, or oral corticosteroid
• Assessment for pulmonary rehabilitation
• Assessment for lung volume reduction surgery or for lung transplantation
• Aged under 40 years or a family history of alpha 1-antitrypsin deficiency
• Haemoptysis: exclude carcinoma of the bronchus

References Used

1. NICE. Chronic Obstructive Pulmonary Disease. National clinical guideline on management of chronic obstructive pulmonary disease in adults in primary and secondary care: Diagnosing COPD. Thorax March 2004; 59 (Suppl 1): i27-i38.

Internet and Further Reading

• GPIAG General Practice in Airways Group
• Global initiative for COPD (Gold)
• BTS British Thoracic Society
• Oxford Textbook of Medicine 4th edition. Chapter 17.18 Chronic Obstructive pulmonary Disease

Acknowledgements EMIS is grateful to Dr Colin Tidy for writing this article. The final copy has passed peer review of the independent Mentor GP authoring team. ©EMIS 2005.

Last issued 05 Jul 2006