High sensitive Assay

The BÜHLMANN ACE high sensitive assay is designed to quantify reproducibly increased ACE activity in CSF samples from suspected and confirmed  neurosarcoidotic patients. ACE activity measurement in diluted serum samples is possible as well.

The assay shows a detection limit of 1 U/L and can be applied either on microtiter plates with a kinetic reader or on some clinical chemistry analyzers. The determined dynamic range goes up to 24 U/L. Results can be retrieved within about half an hour.

The standardization of the assay is based on the well established  BÜHLMANN ACE kinetic assay for serum testing (order code: KK-ACK).

The prinicple of the assay is based, as in the ACE kinetic assay, on the cleavage of the synthetic substrate FAPGG into an amino acid derivate and a dipeptide. The kinetic of this cleavage reaction is measured by recording the decreasing absorbance at 340 nm.

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ACE – Angiotensin Converting Enzyme

ACE is a membrane-bound glycoprotein produced by epithelioid cells of granulomatous tissue and was first reported to be increased in CSF in patients with neurosarcoidosis in the mid-1980s by Schweisfurth et al. Elevated levels understandably occur with other granulomatous diseases (typically rare in neurologic practice) but reports also suggest increased levels in association with CNS tumors and infections such as meningitis.

Neurosarcoidosis

Sarcoidosis is a multisystem granulomatous disorder of unknown etiology and can be present in any organ system. Most commonly it occurs in lungs, followed by the eyes and integument. Nervous system involvement is present in approximately 5% of cases. Multiorgan involvement is a strong clue pointing to sarcoidosis, but the disease may be restricted to the nervous system. Diagnosis may be difficult, or at least delayed, because the clinical presentation and course of the disease is heterogeneous.
A valid, reproducible marker with reasonable sensitivity and specificity for sarcoidosis could influence the degree of pursuit of the diagnosis and likelihood of finding an appropriate biopsy target. A confident diagnosis of neurosarcoidosis requires histologie confirmation of involved nervous system tissue.