When all patients were included in the analysis, S-5-HIAA correlated significantly with tumour load (r = 0.582, P < 0.001), fP-CgA (r = 0.677, P < 0.001), P-proBNP (r = 0.597, P < 0.001) and AIx (r = −0,264, P = 0.035). The gene discussed is NPPB; the disease is neoplasm.