What is the specificity of the Angiotensin-Converting Enzyme (ACE) test for sarcoidosis?

From the Guidelines

The ACE test has limited specificity for diagnosing sarcoidosis, with a specificity of 70% as reported in the european position paper on rhinosinusitis and nasal polyps 2020 1. While elevated serum ACE levels are found in approximately 60% of patients with active sarcoidosis, this test is not specific enough to be used alone for diagnosis. ACE levels can also be elevated in numerous other conditions including tuberculosis, fungal infections, hyperthyroidism, diabetes mellitus, Gaucher's disease, and certain liver diseases. Additionally, ACE levels may be normal in patients with inactive or treated sarcoidosis, further limiting its diagnostic value. The test's utility is primarily as a supportive diagnostic tool when combined with clinical presentation, radiographic findings, and histopathological evidence. Some key points to consider when interpreting ACE test results include:

• The test is not diagnostic on its own, but rather supportive of a diagnosis of sarcoidosis when used in conjunction with other clinical and radiographic findings.
• Elevated ACE levels can be found in other conditions, making it essential to consider alternative diagnoses.
• The test may have more value in monitoring disease activity and response to treatment in patients with established sarcoidosis diagnoses rather than as a primary diagnostic test.
• A definitive diagnosis of sarcoidosis typically requires demonstration of non-caseating granulomas in affected tissues, along with exclusion of other granulomatous diseases, as noted in the american thoracic society clinical practice guideline 1. It's also worth noting that other studies, such as the american thoracic society clinical practice guideline 1, provide additional context and guidance on the diagnosis and detection of sarcoidosis, but the most relevant and recent information on the specificity of the ACE test is found in the european position paper on rhinosinusitis and nasal polyps 2020 1.

From the Research

Specificity of the ACE Test for Sarcoidosis

The specificity of the Angiotensin-Converting Enzyme (ACE) test for sarcoidosis is a measure of its ability to correctly identify those without the disease.

• The study by 2 found a specificity of 93% for the ACE test, indicating that 93% of patients without sarcoidosis were correctly identified.
• In contrast, the study by 3 reported a specificity of 89.9%, which is slightly lower.
• Another study by 4 found a specificity of 83.8%, which is lower than the other two studies.
• The study by 5 discussed the limitations of the ACE test, including its sensitivity and specificity, but did not provide a specific value for specificity.
• The study by 6 found that serum ACE was elevated in 34% of patients with sarcoidosis, but did not provide a direct measure of specificity.

Factors Affecting Specificity

The specificity of the ACE test can be influenced by various factors, including:

• The presence of other diseases, such as military tuberculosis and silicosis, which can cause false positive results 4.
• The stage and activity of the disease, with higher ACE levels often associated with active disease 2, 4.
• The use of steroid therapy, which can affect ACE levels 2, 4.

Clinical Utility

Despite its limitations, the ACE test can still be a useful adjunct to the diagnosis and management of sarcoidosis.

• The study by 4 found that ACE levels correlated well with disease activity and were helpful in patient management.
• The study by 2 reported that the ACE test had a positive predictive value of 93% and a negative predictive value of 74%, indicating that it can be useful in confirming or ruling out the diagnosis of sarcoidosis.