Neuron-specific enolase in non-neoplastic lung diseases, a marker of hypoxemia?

Neuron-specific enolase (NSE) is a glycolytic enzyme localized within neuronal and neuroendocrine tissues. Serum NSE is widely used as a marker of neuroendocrine tumors. Moderate serum NSE elevation has been reported in some patients with benign lung diseases. We decided to investigate whether the elevation of serum NSE in non-neoplastic lung diseases is connected with hypoxemia and to what extent the recovery of sufficient ventilation with a respirator may influence NSE concentrations. Serum NSE was estimated by means of radioimmunoassay in 83 patients with various non-neoplastic lung diseases. Serum NSE exceeding 12.5 micrograms/L was significantly more frequent in patients with marked hypoxemia (PaO2 < 6.67 kPa; p = 0.03) than in others. The median NSE value in the group of patients without respiratory failure (Ro) was 7.2 micrograms/L (10% > 12.5 micrograms/L), in the group of patients with respiratory failure not requiring mechanical ventilation (Rf) it was 8.5 micrograms/L (24% > 12.5 micrograms/L), and in the group of patients with respiratory failure requiring mechanical ventilation (Rfv) 13.1 micrograms/L (60% > 12.5 micrograms/L). The differences between the Rfv group and the other two groups (Rf and Ro) were significant (P = 0.049 and p = 0.0004, respectively). During successful mechanical ventilation elevated serum NSE decreased to values below the cutoff in 8/10 patients. We conclude that serum NSE elevation is a frequent event in patients with terminal hypoxemia in the course of benign lung diseases. Normalization of serum NSE is observed in the majority of patients during the first week of mechanical ventilation.