What is the role of the Angiotensin-Converting Enzyme (ACE) blood test in diagnosing sarcoidosis?

From the Guidelines

The ACE blood test is a useful but not definitive diagnostic tool for sarcoidosis, and its results should be interpreted in conjunction with clinical presentation, imaging, and histological findings, as recommended by the American Thoracic Society clinical practice guideline 1.

Diagnostic Considerations

When evaluating a patient for sarcoidosis, it is essential to consider the clinical features supportive of the diagnosis, including history, physical examination, imaging, and other testing, as outlined in the American Thoracic Society clinical practice guideline 1. The ACE blood test can be a helpful adjunct in the diagnosis of sarcoidosis, but it is not sufficient for diagnosis on its own.

Test Characteristics

Elevated ACE levels are found in approximately 60-80% of patients with active sarcoidosis, with normal levels ranging from 8-53 U/L, and elevated levels typically ranging from 70-150 U/L 1. However, ACE levels can also be elevated in other conditions, limiting its specificity.

Clinical Application

For accurate diagnosis, the ACE test should be interpreted alongside clinical presentation, chest imaging, pulmonary function tests, and tissue biopsy showing non-caseating granulomas. ACE levels can also be useful for monitoring disease activity and treatment response in established sarcoidosis cases, with decreasing levels often indicating improvement.

Key Points

• The ACE blood test is not definitive for diagnosing sarcoidosis
• ACE levels should be interpreted in conjunction with clinical presentation, imaging, and histological findings
• Elevated ACE levels are found in approximately 60-80% of patients with active sarcoidosis
• ACE levels can be elevated in other conditions, limiting its specificity
• The test is useful for monitoring disease activity and treatment response in established sarcoidosis cases, as recommended by the European position paper on rhinosinusitis and nasal polyps 2020 1.

From the Research

Ace Blood Test for Sarcoidosis

• The Ace blood test is used to diagnose and monitor disease activity in sarcoidosis 2, 3.
• Elevated levels of serum angiotensin-converting enzyme (ACE) are not specific for sarcoidosis, but can be used to indicate disease activity 3.
• A study found that serum ACE levels correlated best with clinical status and gallium scans, and less with chest x-ray films and pulmonary function tests (PFTs) 2.
• The best cut-off value for serum ACE levels to detect sarcoidosis was found to be 14.7 IU/L, with a sensitivity of 78.1% and specificity of 81.7% 4.

Correlation with Other Tests

• Serum ACE levels were found to correlate with pulmonary function tests, such as %V25 and V50/V25, at an early stage of the disease 5.
• High-resolution computed tomography (HRCT) scans were found to be better than chest X-radiography for demonstrating patchy increase in density and distinguishing nodules from septal thickening 6.
• HRCT features, such as small nodules and patchy focal increase in lung density, were found to correlate with active alveolitis and the presence of granulomata on histology 6.

Monitoring Disease Activity

• Serial measurements of serum ACE were found to be a sensitive means for following the clinical course of patients with sarcoidosis and predicting clinical relapse or improvement 2.
• ACE levels were found to decrease significantly after the initiation of immunosuppressive therapy, indicating the efficacy of treatment 4.