Why is a Differential Diagnosis Important?
In her article, Differential Diagnosis: What Else Might Your Illness Be?, About.com's Patient Empowerment Guide explains the importance of knowing each differential diagnosis that your doctor has eliminated before reaching a conclusion that you have COPD. This confirms that the evidence he or she used to form your diagnosis was accurate.
You may also want to write down the names of the conditions that your doctor rejected. This way, if your treatment is ineffective, you can revisit the list to see if you were possibly misdiagnosed, which is more common than many of us would like to think.
Characteristic Features of COPD
There are several distinguishing features that may alert your doctor to lean toward a diagnosis of COPD:
- Onset generally occurs during mid-life
- COPD symptoms are progressive and don't go away between exacerbations
- Long-term smoking history is number one risk factor
- Dyspnea occurs with exertion
- Airflow limitation, by and large, is irreversible
Other Possible Causes for Your Symptoms
A diagnosis of COPD should be considered in any patient who complains of dyspnea, long-term cough and/or sputum production with a history of repeated exposure to noxious stimuli. But what about illnesses whose symptoms closely mimic those of COPD? The following are potential diagnoses that may be included in a differential diagnosis:
Asthma
One of the most common differential diagnoses of COPD is asthma. In some cases, it is virtually impossible to tell the two apart, which makes management of either disease difficult. Here are some characteristic features of asthma:
- Onset generally occurs during early life
- Symptoms vary daily, often disappearing between attacks
- Familial history of asthma is often present
- Allergies, rhinitis, and/or eczema may accompany diagnosis
- Unlike COPD, airflow limitation is essentially reversible
Congestive Heart Failure
Congestive heart failure (CHF) is a condition that occurs when the heart is unable to pump blood strongly enough throughout the body to maintain circulation. This causes a backup of fluids in both the lungs and the rest of the body. Symptoms of CHF include dyspnea with activity, cough, weakness and fatigue, all of which are also found in COPD. Featured characteristics of the disease include:
- Fine crackles at base of lungs when listening with a stethoscope
- Chest X-ray shows dilation of heart muscle and pulmonary edema
- Pulmonary function tests show volume restriction, not airflow limitation as seen in COPD
Bronchiectasis
Often caused by recurrent inflammation and infection of the airways, bronchiectasis may be congenital (present at birth) or a person may be predisposed to it as a result of early childhood diseases, such as pneumonia, measles, influenza or tuberculosis. Bronchiectasis is considered an obstructive lung disease and may exist alone or with other forms of COPD. Features include:
- Large amounts of tenacious, purulent sputum
- Generally associated with bouts of repeated bacterial infections
- Coarse crackles heard when listening with stethoscope
- Chest X-ray shows dilated bronchial tubes and thickened bronchial walls
- Clubbing of the fingers
Tuberculosis
Tuberculosis (TB) is a highly contagious bacterial infection caused by the organism Mycobacterium tuberculosis. While the bacteria normally affects the lungs, it can spread to other parts of the body as well, including the brain, kidneys, bones and lymph nodes. Because symptoms include weight loss, fatigue, persistent cough, difficulty breathing, thick or bloody sputum, and chest pain, it is not surprising to see why this illness would be included in a differential diagnosis of COPD. Suggested characteristics of TB are as follows:
- Onset can occur at any age
- Chest X-ray shows air spaces that are filled with fluid (pulmonary infiltrates) and nodular lesions
- Microbiology reports confirm presence of Mycobacterium tuberculosis in sputum and/or blood
- Prevalence of TB within local community
Obliterative Bronchiolitis
Obliterative bronchiolitis is a rare form of bronchiolitis that can be life-threatening. It occurs when the small airways of the lungs, also known as bronchioles, become inflamed, and subsequently compressed and narrowed by scar tissue. Also known as bronchiolitis obliterans, the disease is characterized by airway obstruction and a reduction of FEV1 to as low as 16 percent. Symptoms, like COPD, include dyspnea, cough and wheezing. The disease is characterized as follows:
- Occurs generally at a young age in nonsmokers
- Possible history of rheumatoid arthritis or exposure to toxic fumes
- CT scan shows areas of hypo-density
Diffuse Panbronchiolitis
A severe, progressive form of bronchiolitis, diffuse panbronchiolitis has no known cause and is inflammatory in nature. Similar to COPD, symptoms include dyspnea, wheezing, severe cough and sputum production. If left untreated, diffuse panbronchiolitis may progress to bronchiectasis. Featured characteristics of this type of bronchiolitis are:
- Occurs primarily in nonsmoking males
- Most patients also suffer from long-term sinusitis
- Chest X-ray and CT scan show hyper-inflated lungs and pus and/or fluid-filled lesions
Final Thoughts About Differential Diagnosis of COPD
Because each patient is unique and the course of a disease varies individually, not every illness mentioned above will manifest itself in the same way. This is why it is important to discuss your symptoms with your health care provider as soon as possible so that a proper diagnosis of COPD can be made or ruled out, if warranted.
Source:
Global Initiative for Obstructive Lung Disease. Pocket Guide to COPD Diagnosis, Management and Prevention. Updated 2009.
