Diagnosis of COPD: Required Testing
Spirometry is the essential test required to establish a diagnosis of COPD, with a post-bronchodilator fixed ratio of FEV1/FVC less than 0.70 being the spirometric criterion for airflow limitation. 1
Key Clinical Indicators for COPD Testing
Before proceeding to diagnostic testing, consider COPD in individuals over 40 years with any of these indicators:
- Progressive dyspnea that worsens with exercise and persists over time 1
- Chronic cough (may be intermittent and unproductive) 1
- Chronic sputum production 1
- Recurrent lower respiratory tract infections 1
- History of risk factors (smoking, occupational exposures, genetic factors) 1
Diagnostic Algorithm
Step 1: Medical History Assessment
- Document smoking history (pack-years) and occupational/environmental exposures 1
- Record exercise tolerance to monitor future changes in breathlessness 1
- Assess past medical history including childhood respiratory conditions 1
- Evaluate family history of COPD or other respiratory diseases 1
- Document presence of comorbidities 1
Step 2: Physical Examination
- Physical examination alone is rarely diagnostic in COPD 1
- Signs of airflow limitation/hyperinflation usually only appear with significantly impaired lung function 1
- In severe disease, look for signs of chronic overinflation, wheezing on forced expiration, and potential signs of cor pulmonale 1
Step 3: Spirometry (Required for Diagnosis)
- Perform post-bronchodilator spirometry to confirm airflow obstruction 1
- Diagnostic criteria: FEV1 <80% predicted AND FEV1/FVC ratio <70% 1
- A normal FEV1 effectively excludes the diagnosis 1
Step 4: Bronchodilator Reversibility Testing
- Perform to differentiate COPD from asthma and establish post-bronchodilator FEV1 1
- A positive response is considered when FEV1 increases by 200 ml and 15% of baseline value 1
- Substantial bronchodilator response suggests possibility of asthma 1
Step 5: Additional Testing (As Indicated)
- Chest radiography: Not needed for diagnosis of mild COPD but indicated if another diagnosis is being considered 1
- CT scanning: Can help differentiate between structural abnormalities causing airflow limitation and identify comorbidities 1
Common Pitfalls in COPD Diagnosis
- Overdiagnosis: Up to one-third of patients diagnosed with COPD may be misdiagnosed when confirmatory spirometry is not performed 2
- Reliance on symptoms alone: Symptoms of dyspnea, cough, and wheeze are nonspecific and can be attributed to various diseases 3, 2
- Misclassification in elderly: The fixed FEV1/FVC ratio may result in more frequent diagnosis of COPD in elderly patients 1
- Underdiagnosis: Due to progressive nature of disease, underestimation of symptoms by patients, and underuse of spirometry by primary care providers 4
Factors That May Lead to Misdiagnosis
- Higher BMI (more likely to have restrictive pattern) 2
- Multiple comorbidities 2
- Less extensive smoking history 2