Diagnosing COPD

Chronic obstructive pulmonary disease (COPD) 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, usually in patients with a smoking or passive smoking history, and supported by spirometry.¹

There are separate articles covering Chronic Obstructive Pulmonary Disease, the Management of Stable COPD, Acute Exacerbations of COPD and Use of Oxygen Therapy in COPD.

Presentation¹

• 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 spirometry.

• 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 symptoms:
  

  • 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 breathless, ankle swelling, fatigue. Also ask about chest pain and haemoptysis which are unusual symptoms in COPD and should prompt consideration of an alternative diagnosis.

The Medical Research Council (MRC) dyspnoea scale should be used to grade the level of breathlessness:

• Not troubled by breathlessness except on strenuous exercise.

• Short of breath when hurrying or walking up a slight hill.

• Walks slower than contemporaries on level ground because of breathlessness or has to stop for breath when walking at own pace.

• Stops for breath after walking about 100 m or after a few minutes on level ground.

• 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 present:

• Cachexia.

• Hyperinflated chest, pursed lip breathing, use of accessory muscles, paradoxical movement of lower ribs, reduced cricosternal distance.

• Wheeze or quiet breath sounds.

• Reduced cardiac dullness on percussion.

• Peripheral oedema.

• Cyanosis.

• Raised jugular venous pressure (JVP).

Investigations: spirometry^{1 2}

Spirometry should be performed in patients with features suspicious of COPD. Specifically in those who are aged over 35, are current or ex-smokers (or have a history of exposure to other risk factors such as air pollutants), and who have a chronic cough and/or one of the other typical symptoms listed above. Spirometry should be also considered in patients with chronic bronchitis. A significant proportion of these will go on to develop airflow limitation.

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. It is also used to monitor the progression of the disease. It does not, however, necessarily correlate well with symptom severity and impact on the quality of life, so other factors discussed below have to be taken into account in order to make a full assessment.

Assessment is based on post-bronchodilator measurements. A diagnosis of airflow obstruction can be made for forced expiratory volume in one second (FEV1)/forced vital capacity (FVC) less than 0.7 (ie 70%) and FEV1 less than 80% predicted.

National Institute for Health and Care Excellence (NICE) classification of the severity of COPD:

• Stage 1: mild - FEV1 is >80% predicted.

• Stage 2: moderate - FEV1 is 50-79% predicted.

• Stage 3: severe - FEV1 is 30-49% predicted.

• Stage 4: very severe - FEV1 is below 30% predicted (or FEV1 less than 50% but with respiratory failure).

The 2012 Global Lung Initiative reference values are used, but it is recognised that these are not applicable to all ethnic groups, although the age range now extends to 93.³

Reversibility testing is not needed as part of the routine diagnostic process in most people. In most cases the diagnosis of COPD is suggested by the combination of the clinical history, signs and post-bronchodilator spirometry. 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.

See also the separate Spirometry Calculator article.

Further investigations^{1 2}

At the time of their initial diagnostic evaluation, in addition to spirometry all patients should have:

• CXR to exclude other pathologies.

• FBC to identify anaemia or polycythaemia.

• BMI calculated.

Additional investigations should be performed to exclude alternative diagnoses and comorbidity and 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.

• Measurement of carbon monoxide transfer factor: 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 CXR and assess suitability for surgery. Note that the presence of emphysema on CT scan is an independent risk factor for lung cancer.

• ECG and echocardiography: to assess cardiac status if there are features of heart disease or pulmonary hypertension.

• Sputum culture: to identify organisms if sputum is persistently present and purulent.

Assessing severity and prognosis

Spirometry correlates poorly with symptoms and the impact on quality of life. A true assessment of severity should include not only an assessment of the degree of airflow obstruction, but also the impact on the person, the risk of exacerbations and admissions, and the threat to life. This will help to guide management and prognosis. Include in the assessment:

• Spirometry results.

• Breathlessness (MRC scale) - see above.

• Symptom burden. The COPD Assessment Test (CAT test) score may be helpful.^{4 5}

• Body mass index (BMI)

• Exercise capacity.

• Severity and frequency of exacerbations and need for hospital admission.

• Chronic hypoxia and/or cor pulmonale.

• Co-morbidity/multi-morbidity.

• Smoking status.

• Frailty.

Differential diagnosis^{1 2}

• Asthma.

• Bronchiectasis.

• Congestive cardiac failure.

• Lung cancer.

• Obliterative bronchiolitis.

• Bronchopulmonary dysplasia.

• Tuberculosis.

Is it COPD or asthma?

Clinical features which help differentiate include:

• Age at onset: usually younger in asthma.

• Smoking history: in most with COPD.

• Variability in symptoms: breathlessness is variable in people with asthma; persistent and progressive in COPD. In those with asthma, breathlessness varies between day and night and day to day.

• Nocturnal symptoms: more common in asthma.

• Presence of persisting productive cough: common in COPD but not in asthma.

Longitudinal observation of patients (whether using spirometry, peak flow or symptoms) may be needed 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 400 ml) response to bronchodilators.

• Large (over 400 ml) response to 30 mg oral prednisolone daily for two 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.