From the Guidelines
Dyspnea of unknown origin (DUO) is the diagnosis of exclusion for unexplained shortness of breath after comprehensive evaluation has ruled out common causes, and a thorough history and physical examination, along with targeted diagnostic tests, are essential in evaluating patients with dyspnea. When evaluating a patient with dyspnea, it is crucial to exclude cardiac causes (heart failure, coronary artery disease, valvular disease), pulmonary conditions (COPD, asthma, interstitial lung disease, pulmonary embolism, pneumonia), anemia, deconditioning, and obesity, as these are common causes of dyspnea 1. The diagnostic approach should include:
- A thorough history and physical examination to identify potential causes of dyspnea
- Chest imaging (X-ray and possibly CT) to evaluate for pulmonary causes
- Pulmonary function tests to assess lung function
- Complete blood count and basic metabolic panel to evaluate for anemia and other potential causes
- ECG and echocardiogram to evaluate for cardiac causes Additional tests may include cardiopulmonary exercise testing, bronchoscopy, or right heart catheterization depending on clinical suspicion 1. Management focuses on treating any identified underlying causes, and if no specific cause is found despite thorough evaluation, supportive measures like pulmonary rehabilitation, breathing techniques, and in some cases, low-dose anxiolytics may help manage symptoms 1. Periodic reassessment is important as new diagnostic clues may emerge over time, and a systematic evaluation is necessary to ensure no treatable causes are missed.
From the Research
Diagnosis of Exclusion for Dyspnea
The diagnosis of exclusion for dyspnea involves a systematic approach to rule out potential causes of the symptom. The following steps can be taken:
- A detailed history and physical examination should be conducted to identify potential causes of dyspnea 2
- First-line tests such as complete blood count, basic chemistry panel, electrocardiography, chest radiography, spirometry, and pulse oximetry can be used to evaluate the patient 2
- If no cause is identified, second-line noninvasive testing such as echocardiography, cardiac stress tests, pulmonary function tests, and computed tomography scan of the lungs can be considered 2
- The use of biomarkers such as natriuretic peptides can be helpful in ruling out heart failure, particularly if the level is <100 pg/ml 3
Diagnostic Tools
Various diagnostic tools can be used to evaluate dyspnea, including:
- Lung ultrasound, which has a sensitivity of 57.73% and specificity of 87.97% for diagnosing acute heart failure 4
- Chest X-ray, which has a sensitivity of 74.49% and specificity of 86.26% for diagnosing acute heart failure 4
- NT pro-BNP level determination, which has a sensitivity of 97.59% and specificity of 27.56% for diagnosing acute heart failure 4
- Combining chest X-ray and lung ultrasound can provide the best overall performance with 84.69% sensitivity, 77.69% specificity, and 87.07% negative predictive value 4
Approach to Diagnosis
A stepwise workup combining chest X-ray and lung ultrasound at first, then for those negative, a determination of NT pro-BNP assay would be a reasonable approach to the dyspneic patient 4 The primary care physician can play a key role in managing patients with chronic dyspnea, and a multidisciplinary approach is often necessary 2 Urgent transfer from the general practice setting to a more specialised centre is usually necessary for patients with acute dyspnoea 5