Chronic Obstructive Pulmonary Disease (COPD) is a progressive condition characterized by persistent airflow limitation and chronic inflammation in the lungs. It is a major global health concern, yet it remains one of the most frequently misdiagnosed respiratory illnesses. Studies suggest that between 60% and 86% of people with the condition may be underdiagnosed, missing opportunities for early intervention. The rate of overdiagnosis is also high, ranging from 5% to 60% worldwide, resulting in unnecessary and potentially harmful therapies. This dual problem highlights the challenges clinicians face in distinguishing COPD from conditions that present with similar symptoms.
The Gold Standard Diagnostic Process
An accurate diagnosis of COPD relies on a thorough patient history combined with spirometry. The patient history focuses on exposure to noxious particles or gases, such as smoking, occupational, and environmental exposures. Symptoms like chronic cough, sputum production, and progressive breathlessness are noted, especially if they are persistent.
Spirometry is the tool for confirming airflow obstruction, the defining feature of COPD. During this test, the patient exhales forcefully into a device that measures the Forced Expiratory Volume in one second (FEV1) and the Forced Vital Capacity (FVC). The Global Initiative for Chronic Obstructive Lung Disease (GOLD) standard requires a post-bronchodilator FEV1/FVC ratio of less than 0.70.
The post-bronchodilator value measures airflow limitation after the airways have been maximally opened by a short-acting inhaler medication. If the FEV1/FVC ratio remains below 0.70, the obstruction is considered fixed and poorly reversible, confirming the diagnosis. This measurement separates true COPD from other respiratory conditions.
Conditions Frequently Mistaken for COPD
The most common reason for misdiagnosis is the significant overlap in symptoms, such as shortness of breath and chronic cough, between COPD and several other cardiopulmonary disorders. Differentiating these conditions requires careful clinical assessment beyond simple symptom presentation.
Asthma
Asthma is frequently confused with COPD, particularly in older patients who smoke, a condition sometimes referred to as Asthma-COPD Overlap (ACO). The key differentiator is the reversibility of the airflow limitation. In asthma, the obstruction is highly variable and often fully reversible, meaning the FEV1/FVC ratio returns to a normal range after bronchodilator administration. Spirometry demonstrating an increase in FEV1 of at least 12% and 200 milliliters following bronchodilator use suggests asthma. COPD involves chronic airway inflammation and structural damage that results in persistent, irreversible airflow limitation.
Bronchiectasis
Bronchiectasis is a separate lung disease characterized by permanent, abnormal widening and scarring of the airways, leading to chronic infection and excessive mucus production. While this condition causes a chronic cough and sputum like COPD, it is defined by anatomical damage rather than fixed airflow limitation. A definitive diagnosis requires a High-Resolution Computed Tomography (HRCT) scan of the chest, which confirms bronchial dilation and wall thickening. Spirometry alone is insufficient to diagnose bronchiectasis; the structural damage seen on HRCT is the distinguishing feature.
Congestive Heart Failure
Congestive Heart Failure (CHF) often presents with shortness of breath and fatigue, symptoms that can be mistaken for COPD, especially in older adults with shared risk factors like smoking. The wheezing associated with fluid buildup in the lungs from CHF is sometimes called “cardiac asthma.” CHF is a cardiac problem and often includes symptoms like orthopnea (difficulty breathing when lying flat), swelling in the legs (pedal edema), and elevated blood pressure. Specialized testing, such as a blood test for Brain Natriuretic Peptide (BNP) levels and an echocardiogram, is necessary to confirm the cardiac origin.
Systemic and Testing Errors Leading to Misdiagnosis
Beyond the challenges of symptom overlap, errors in the execution and interpretation of the diagnostic process contribute to COPD misdiagnosis. The underutilization of spirometry is a systemic failure, as many diagnoses are made solely on symptoms and patient history without objective confirmation. When spirometry is not performed, patients may be overdiagnosed with COPD, leading to unnecessary inhaler prescriptions.
Even when spirometry is used, poor technique can yield inaccurate results, as the test is dependent on the patient’s maximal effort. Misinterpretation of spirometry data is a common error, with one study finding this to be the leading cause of misdiagnosis. Clinicians may mistakenly rely on the pre-bronchodilator FEV1/FVC ratio, which can be abnormally low due to temporary bronchoconstriction, leading to a false-positive diagnosis of fixed obstruction.
The use of a fixed ratio of 0.70 for diagnosis can contribute to overdiagnosis, particularly in older adults who naturally experience a decline in lung function with age. This fixed threshold may label a person with physiologically normal aging as having COPD, even when results fall within the expected range for their age group. Conversely, failure to adjust spirometry results for factors like ethnicity can contribute to the underdiagnosis of COPD in some populations.
Next Steps: Seeking a Confirmed Diagnosis
For people who suspect their COPD diagnosis may be incorrect, or who have been diagnosed without spirometry, the next step is to seek a definitive assessment. It is advisable to obtain a second opinion from a pulmonologist, a physician specializing in lung conditions. These specialists have the expertise to interpret complex pulmonary function tests and distinguish between mimicking conditions.
Patients should ensure that a full post-bronchodilator spirometry test is performed and interpreted by a trained professional using current international guidelines. Tracking symptoms, including specific triggers, the variability of shortness of breath, and non-respiratory symptoms like leg swelling, provides invaluable information. Providing the specialist with detailed symptom logs helps accurately differentiate between a fixed obstructive disease like COPD and a reversible condition like asthma or a cardiac issue.