Cerebrospinal fluid angiotensin-converting enzyme for diagnosis of central nervous system sarcoidosis

Background: Sarcoidosis is a multisystem granulomatous disease that may involve the central nervous system (CNS) in many ways, leading to diagnostic difficulties. An accurate diagnostic laboratory test would enhance the evaluation and management of these patients. Objective: To determine the diagnostic accuracy of cerebrospinal fluid angiotensin-converting enzyme (ACE) for CNS neurosarcoidosis. Methods: The objective was addressed through the development of a structured critically appraised topic. This included a clinical scenario, structured question, search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions. Participants included consultant and resident neurologists, a medical librarian, clinical epidemiologists, and content experts in the field of neuroimmunology. Results: Two primary articles were selected for review. Cerebrospinal fluid ACE assay is insensitive (24%-55%) but may be reasonably specific (94% - 95%) for CNS neurosarcoidosis. However, existing data are derived from studies with significant methodological and reporting limitations. Conclusions: The diagnostic accuracy of cerebrospinal fluid ACE for CNS neurosarcoidosis is not clearly established and the test cannot replace tissue diagnosis. Despite its insensitivity, some clinicians might consider the specificity of cerebrospinal fluid ACE, based on existing data, high enough to warrant inclusion in the diagnostic evaluation of patients in whom CNS neurosarcoidosis is being considered. A well-designed prospective diagnostic study seems warranted.