The diagnostic value of neuron-specific enolase and carcino-embryonic antigen analyses in patients with carcinoma of the lung.

Neuron-specific enolase and carcino-embryonic antigen were quantified simultaneously in sera of 135 patients attending the Department of Respiratory Diseases for diagnostic bronchoscopy. Fifteen small cell lung carcinomas, 24 non-small cell lung carcinomas and 96 benign pulmonary diseases were investigated. Lung biopsies or bronchial washings were obtained from about 75% of the patients, including all patients with neoplastic diseases. Serum neuron-specific enolase was measured by a recently introduced enzyme-immuno assay (WaKo NS-Enolase EIA-II testkit). The results obtained with this kit were similar to those based on RIA assays. Receiver Operating Characteristic curves (ROC curves) were constructed for comparison of the discriminating ability of neuron-specific enolase and carcino-embryonic antigen in small cell lung carcinomas and non-small cell lung carcinomas. For small cell lung carcinomas the sensitivity and the specificity of neuron-specific enolase (cutoff value: 10 micrograms/l) were 87% and 88%, respectively, and for carcino-embryonic antigen values 60% and 77% were obtained. There was no correlation between neuron-specific enolase and carcino-embryonic antigen in small cell lung carcinoma patients. The diagnostic value of neuron-specific enolase and carcino-embryonic antigen in non-small cell lung carcinomas is illustrated by sensitivities of 13% and 58%, respectively. An extensive literature survey is included to allow comparison with other studies. The use of ROC curves is recommended for the determination of optimal cutoff values for the assays employed.