Neuron-Specific Enolase (NSE), Spinal Fluid

CPT CODE:

USEFUL FOR:

An auxillary test in the diagnosis of Creutzfeldt-Jakob disease
An auxillary test in the diagnosis of small cell lung carcinoma (SCLC)metastasis to central nervous system or leptomeninges

SPECIMEN REQUIRED:

0.5 mL of spinal fluid. Send specimen refrigerated.

TRANSPORT TEMPERATURE:

Refrig\Ambient <=3 days OK\Frozen NO 

CLINICAL INFORMATION:

Enolase is a glycolytic enzyme that catalyzes the conversion of 2-phosphoglycerate to phosphoenolpyruvate. Enolase exists in theform of several tissue-specific isoenzymes, consisting of homo orheterodimers of 3 different monomer-isoforms (alpha, beta, andgamma). Neuron-specific enolase (NSE) is a 78 kD gamma-homodimerand represents the dominant enolase-isoenzyme found in neuronaland neuroendocrine tissues. Its levels in other tissues, excepterythrocytes, are negligible. The biological half-life of NSE in bodyfluids is approximately 24 hours.
Due to this organ-specificity, concentrations of NSE in serum or, morecommonly, cerebrospinal fluid (CSF) are often elevated in diseaseswhich result in relative rapid (hours/days to weeks, rather than monthsto years) neuronal destruction. Measurement of NSE in serum or CSFcan therefore assist in the differential diagnosis of a variety of neuron-destructive and neurodegenerative disorders. The most commonapplication is in the differential diagnosis of dementias, where elevatedCSF concentrations support the diagnosis of rapidly progressivedementias, such as Creutzfeldt-Jakob disease (CJD). NSE might alsohave utility as a prognostic marker in neuronal injury. There is, forexample, increasing evidence that elevated serum NSE levelscorrelate with a poor outcome in coma, in particular when caused byhypoxic insult.

CLINICAL INTERPRETATION:

The diagnosis of CJD is highly complex and involves clinical historyand neurologic examination, detection of characteristic periodic sharpand slow wave complexes on electroencephalographs, magnetic resonance imaging (hyperintense basal ganglia), and exclusion ofother possible causes of dementia, in addition to CSF examination.Consequently, patients are often diagnosed as having possible,probable, or definite CJD based upon the constellation of clinicalfindings. Detection of elevated CSF levels are NSE protein in thesepatients assists in the final diagnosis.
A CSF NSE within the normal reference range makes sporadic CJDvery unlikely, but can be observed in less rapidly progressive forms of CJD, such as variant CJD related to infection with prions that causebovine spongiform encephalopathy. With the previous Mayo Clinic-developed assay, in a group of carefully pre-selected patients with aprobable diagnosis of CJD and an indeterminate or elevated NSEconcentration in CSF, the respective diagnostic sensitivities ofapproximately 87% and approximately 80%, and diagnosticspecificities of approximately 66% and approximately 83% wereobserved.
SCLC CNS metastases, particularly if they involve the leptomeniges, will lead to, usually substantial, elevations in CSF NSE concentrations.

REFERENCE VALUES:

Normal: <=15 ng/mL

Indeterminate: 15-30 ng/mL

Elevated: >30 ng/mL

Elevated results may indicate the need for additional work-up.

Possible causes may be NSE-secreting CNS/Leptomeningeal

tumor or rapid neuronal destruction from a variety of causes. In the

context of dementia, elevated results may be suggestive of

Creutzfeldt-Jakob disease