Best for diagnosing carcinoid tumour is

Conventional tumour pathology criteria and dna cytometry have limited value in assessing the malignancy of a neuroendocrine tumour. Hence, the detection of substances that are more specific for carcinoid tumours can facilitate a more exact diagnosis. Two markers are primarily used to diagnose and follow carcinoid tumours: 5-hydroxy-indole-acetic acid (5-hiaa) and chromogranin A (CgA). Serotonin released by carcinoid tumours is metabolized by monoamine oxidases in the liver, lungs, and brain to 5-hiaa. When measured in a 24-hour urine sample, 5-hiaa level has a sensitivity of 73% and a specificity of 100% for diagnosing carcinoid . The normal range for urinary 5-hiaa is 3-15 mg/24 h, but the figure may vary depending on the laboratory . Chromogranin A is found in the wall of synaptic vesicles that store serotonin and glucagons. Levels of CgA tend to correlate with tumour bulk but not with symptoms. In general, CgA levels are elevated in 85%-100% of patients with carcinoid tumour, regardless of whether the tumour is functional or nonfunctional. Ref - pubmed.com