What are the laboratory tests for Sarcoidosis (a systemic granulomatous disease)?

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 serum soluble interleukin-2 (sIL-2R), lysozyme levels, and fluorodeoxyglucose-positron emission tomography (FDG-PET) to evaluate disease activity. When diagnosing sarcoidosis, it is essential to consider a combination of clinical, radiological, and histological evidence of non-caseating granulomas. Some key laboratory tests and their implications include:

• Serum ACE levels: often elevated in active sarcoidosis, though this test lacks specificity 1
• Serum sIL-2R and lysozyme levels: useful tools in the diagnosis of sarcoidosis and for evaluating disease activity 1
• FDG-PET: helpful in evaluating disease activity and assessing organ involvement 1
• Blood tests: may include raised serum and urinary calcium levels, raised alkaline phosphatase, but none are diagnostic 1
• Tissue biopsy: definitive diagnosis requires tissue biopsy showing non-caseating granulomas while excluding other granulomatous diseases 1 It is crucial to note that no single test is diagnostic on its own, and a combination of these tests, along with clinical and radiological evaluation, is necessary to diagnose sarcoidosis and assess organ involvement. The diagnosis of sarcoidosis requires a comprehensive approach, considering the patient's clinical presentation, laboratory results, and imaging studies. In clinical practice, the diagnosis of sarcoidosis is often made based on a combination of these factors, and the choice of laboratory tests may vary depending on the individual patient's presentation and suspected organ involvement. For example, pulmonary function tests and chest X-rays may be important in assessing lung involvement, while electrocardiogram and ophthalmologic examination may be necessary to evaluate cardiac and ocular manifestations, respectively. Ultimately, the goal of laboratory testing in sarcoidosis is to support the diagnosis, assess disease activity, and guide treatment decisions to improve patient outcomes.

From the Research

Laboratory Tests for Sarcoidosis

The following laboratory tests are used to diagnose and monitor Sarcoidosis:

• Blood tests, including:
  • Blood count 2
  • Calcium levels 2, 3, 4
  • Creatinine levels 2
  • Transaminases 2
  • Erythrocyte sedimentation rate (ESR) 4, 5
  • Immunoglobulins 4
  • Albumin 4
  • Alkaline phosphatase 4
• Urine tests, including:
  • Calcium levels in 24-hour urine samples 2
• Other tests, including:
  • Angiotensin-converting enzyme (ACE) levels 3, 4, 5, 6
  • Lysozyme 3
  • Beta 2-microglobulin 3
  • Collagenase 3
  • Carboxypeptidase 3
  • Glucuronidase 3
  • Bronchoalveolar lavage fluid analysis 5
  • Biopsy of involved tissues 2, 4, 5
  • Lung function tests 2, 4
  • ECG and ECHO heart tests 2
  • USG abdomen 2
  • Ophthalmoscopic examinations 2, 4
  • 67Ga scanning 4
  • Testing for delayed skin reactions 4

Diagnostic Value of Laboratory Tests

The diagnostic value of these laboratory tests varies:

• Angiotensin-converting enzyme (ACE) levels have a good specificity for diagnosing Sarcoidosis, but poor sensitivity 5, 6
• The combination of clinical, radiological, and histopathological findings is essential for diagnosing Sarcoidosis 2, 4