AFP and squamous cell carcinoma: Another study found that CEA, squamous cell carcinoma (SCC), carbohydrate antigen 50 (CA50) and neuron-specific enolase (NSE) showed high false positive rates compared to normal reference values of the indicators in CRF patients and concluded that these values were unreliable in CRF patients, whereas carbohydrate antigen 125 (CA125), CA153, CA199, alpha-fetoprotein (AFP), prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP) were still specific for assessing tumors in CRF with different cutoff values (Cases et al., 1991).