Table 3: Test Indication.

Test	Indication	Characteristics
Chromogranin A	General marker for NETs	Specificity and sensibility limitations
5-HIAA	Carcinoid syndrome, midgut tumour	Specific for carcinoid syndrome. Particular attention to potential false positive results
Gastrin	Gastric, pancreas and duodenum NETs	Useful for differentiation of stomach NET, indicated for pancreatic or duodenal gastrinoma
Secretin	Complementary to gastrin measurement (when levels are 200–1000 pg/mL)	Difficult to access
Insulin, pro-insulin, C Peptide after 72-h fasting	Insulinoma	Indicated when glycemic levels ≤nd mg/dl and concentration of insulin ≥6 µU/l. Hospitalisation required
Glucagon	Glucagonoma	After 8-h fasting