Efficiency of serum copper/zinc ratio for differential diagnosis of patients with and without lung cancer.

We examined serum copper (Cu), serum zinc (Zn), and the serum copper/zinc ratio (Cu/Zn) in 162 patients. All of them were seen to have an abnormal shadow in the chest X-ray films, that is, 109 patients with lung cancer (LC) and 53 patients with no lung cancer (NLC). The mean Cu and Cu/Zn in LC patients were significantly higher than those in NLC patients (p < 0.05). In LC patients, Cu and Cu/Zn were higher and Zn was lower in advanced tumors than early ones. There was a significantly clear relation between Cu or Cu/Zn and the tumor (T) stages. When the relative risk (RR) of LC was estimated, it was seen that the higher Cu and Cu/Zn became, the higher RR became. Furthermore, we showed the sensitivity of the receiver operator characteristic of the test (ROC) curve for Cu, Cu/Zn, and carcinoembryonic antigen (CEA) to diagnose LC, as explained in a paragraph of methods. The determinations of Cu, Zn, and Cu/Zn are simple and inexpensive. They also appear to have a great diagnostic value in determining the local invasion of LC and as a screening test in the high-risk patients for LC.