Monoclonal immunoradiometric assay and polyclonal radioimmunoassay compared for measuring neuron-specific enolase in patients with lung cancer.

Neuron-specific enolase (NSE) is the most sensitive and specific tumor marker for small-cell lung cancer (SCLC). We evaluated a new monoclonal IRMA (Sangtec) for NSE and compared it with a polyclonal RIA (Pharmacia) in patients with SCLC or other lung cancers (NSCLC). We measured NSE concentrations in 100 healthy subjects (NI group), 100 patients with benign pulmonary diseases (BPD group), and 194 patients with advanced lung cancer (97 SCLC and 97 NSCLC). Intra- and interassay CVs were less than 7% for both assays, and dose-dilution curves paralleled their respective standard curves. Values measured by both assays were highly correlated in all groups. NSE concentrations were significantly (P less than 0.001) lower by IRMA than by RIA in NI and BPD groups. The upper 95th percentile values for NSE in the NI group were 11.7 micrograms/L in the RIA and 9.2 micrograms/L in the IRMA. In NSCLC, the values were significantly (P less than 0.05) lower by IRMA but the percentage of subjects with increased values was higher (vs the NI group, 31% for RIA and 44% for IRMA, P less than 0.005). Diagnostic sensitivity for SCLC was improved with IRMA: 83% of values with RIA and 93% with IRMA were increased above the NI group values (P less than 0.005); the corresponding values for SCLC vs BPD were 81% and 89% (P less than 0.05). NSE values measured in 39 patients with SCLC after chemotherapy were more often increased and were significantly higher with the IRMA than with the RIA (P less than 0.005).