The glycolytic enzyme enolase (2-phospho-D-glycerate hydrolase, EC 4.2.1.11) exists as several dimeric isoenzymes (αα,αβ, αγ, ββ and γγ) composed of three distinct subunits α, β, and γ. The γ-unit is found either in a homologous γγ- or in a heterologous α, γ-isoenzyme and is known as neuron-specific enolase (NSE). The monoclonal antibodies used in the CanAg NSE EIA bind to the γ -subunit of the enzyme and thereby detect both the γγ and the αγ forms.The NSE levels are low in healthy subjects and subjects with benign diseases. Elevated levels are commonly found in patients with malignant tumors with neuroendocrine differentiation, especially small cell lung cancer (SCLC)and neuroblastoma.

Quantitative determination of NSE in serum may be valuable in the management of patients with suspected or diagnosed SCLC or to aid in the differential diagnosis and to monitor the effect of treatment.