What are the laboratory tests for Sarcoidosis (Sarcoidosis is a condition characterized by the growth of granulomas, which are inflammatory cells, in various parts of the body)?

From the Guidelines

Laboratory tests for sarcoidosis should include serum angiotensin-converting enzyme (ACE) levels, as they are the most widely used laboratory test for the investigation of sarcoidosis, in addition to other tests such as complete blood count, comprehensive metabolic panel, and serum calcium levels. According to the european position paper on rhinosinusitis and nasal polyps 2020 1, serum ACE is the most widely used laboratory test for the investigation of sarcoidosis. The diagnosis and detection of sarcoidosis guideline by the American Thoracic Society 1 also suggests baseline serum creatinine testing to screen for renal sarcoidosis, baseline serum alkaline phosphatase testing to screen for hepatic sarcoidosis, and baseline serum calcium testing to screen for abnormal calcium metabolism.

Some key laboratory tests for sarcoidosis include:

• Complete blood count
• Comprehensive metabolic panel
• Serum calcium
• Angiotensin-converting enzyme (ACE) levels
• Liver function tests, as hepatic involvement occurs in 12% of cases, with most having hepatic granulomas 1
• Pulmonary function tests, which often show restrictive patterns with decreased diffusion capacity
• Chest X-ray and high-resolution CT scans, with bilateral hilar lymphadenopathy being a classic finding
• Bronchoalveolar lavage, which typically shows increased lymphocytes with an elevated CD4/CD8 ratio
• Electrocardiogram, ophthalmologic examination, and tuberculin skin test to rule out tuberculosis
• Serum biomarkers like soluble interleukin-2 receptor, neopterin, and chitotriosidase, which are emerging as potentially useful markers but aren't routinely used 1.

The laboratory evaluation should be tailored to the clinical presentation, as sarcoidosis can affect multiple organ systems. Definitive diagnosis requires histological confirmation through tissue biopsy showing non-caseating granulomas.

From the Research

Laboratory Tests for Sarcoidosis

The diagnosis of sarcoidosis is based on a combination of clinical, radiological, and histopathological findings, as well as the exclusion of other diseases with similar presentations 2, 3. Some of the laboratory tests used to diagnose and monitor sarcoidosis include:

• Blood tests, such as:
  • Complete blood count
  • Calcium levels
  • Creatinine levels
  • Transaminases
  • Angiotensin-converting enzyme (ACE) levels, which are often elevated in patients with sarcoidosis 4, 5
• Urine tests, such as:
  • Calcium levels in a 24-hour urine sample
• Imaging studies, such as:
  • Chest X-rays
  • Computed tomography (CT) scans
  • Magnetic resonance imaging (MRI) scans
  • Positron emission tomography (PET) scans
• Biopsy of affected tissues, which can show non-caseating granulomas, a characteristic feature of sarcoidosis 2, 3, 4
• Pulmonary function tests, which can help assess lung involvement 2, 3
• Ophthalmoscopic examinations, which can help detect eye involvement 2, 4
• Electrocardiogram (ECG) and echocardiogram (ECHO) to assess cardiac involvement 2

Biochemical Markers

Several biochemical markers have been studied as potential indicators of disease activity and progression in sarcoidosis, including:

• Serum and urinary calcium levels
• 1,25-dihydroxyvitamin D levels
• Lysozyme levels
• Angiotensin-converting enzyme (ACE) levels
• Beta 2-microglobulin levels
• Collagenase levels
• Carboxypeptidase levels
• Glucuronidase levels 6