From the Guidelines
Investigations for suspected sarcoidosis should include a comprehensive approach to confirm diagnosis and assess organ involvement, with a focus on baseline serum calcium testing, serum alkaline phosphatase testing, and ECG to screen for possible cardiac involvement, as recommended by the American Thoracic Society clinical practice guideline 1. Initial testing should include chest X-ray, pulmonary function tests, and blood tests including complete blood count, comprehensive metabolic panel, calcium levels, and angiotensin-converting enzyme (ACE) levels.
- High-resolution CT scan of the chest provides detailed imaging of lung parenchyma and lymph nodes.
- Tissue biopsy remains the gold standard for diagnosis, typically obtained from the most accessible involved site such as lymph nodes, skin lesions, or lung tissue via bronchoscopy with transbronchial biopsy, as supported by the European position paper on rhinosinusitis and nasal polyps 2020 1.
- Bronchoalveolar lavage showing increased CD4/CD8 lymphocyte ratio supports the diagnosis. Additional organ-specific testing may include:
- Cardiac MRI or PET scan for cardiac involvement
- Ophthalmologic examination for ocular manifestations
- 24-hour urine calcium for renal involvement
- Neuroimaging for neurosarcoidosis
- Tuberculin skin test or interferon-gamma release assay should be performed to exclude tuberculosis, which can mimic sarcoidosis, as noted in the European position paper on rhinosinusitis and nasal polyps 2020 1. Baseline serum calcium testing is recommended to screen for abnormal calcium metabolism, and serum alkaline phosphatase testing is suggested to screen for hepatic sarcoidosis, as recommended by the American Thoracic Society clinical practice guideline 1. These investigations help establish diagnosis, determine disease extent, guide treatment decisions, and provide baseline measurements for monitoring disease progression or response to therapy.
From the Research
Investigations for Sarcoidosis
The following investigations can be used to diagnose and assess sarcoidosis:
- Chest radiography: to assess bilateral hilar lymph node enlargement and interstitial lung disease 2, 3, 4
- Computed Tomography (CT): to evaluate lung parenchyma and disease progression 2, 4, 5
- Magnetic Resonance Imaging (MRI): as a viable alternative to HRCT in assessing lung parenchyma and disease progression 2
- Pulmonary function tests: to assess forced vital capacity (FVC) and diffusing capacity of the lung for carbon monoxide (DLCO) 2, 4, 6
- Cardiopulmonary exercise testing: to evaluate functional capacity and understand the mechanism behind dyspnea of uncertain origin 4, 6
- Six-minute walk test: to assess functional capacity and exercise intolerance 6
- Endoscopic transbronchial needle aspiration: to support diagnosis and obtain biopsy samples 4, 5
- Bronchoalveolar lavage (BAL): to individualize diagnosis, although not decisive for most patients 4
- Biopsy: to provide pathologic evidence of noncaseating granulomas and exclude other diseases with similar findings 3, 4, 5
Diagnostic Criteria
The diagnosis of sarcoidosis relies on: