<prompt> Carcinoid tumor is diagnosed by -Urinary 5 HIAASerum Chromogranin APlasma neuro-specific enolaseUrinary 5-HTP  <response>: Ans. is a i.e., Urinary 5 HIAA Diagnosis of carcinoid syndrome: The diagnosis of carcinoid syndrome relies on measurement of urinary or plasma serotonin or its metabolites in the urine. The measurement of 5-HIAA is used most frequently. False-positive elevations may occur if the patient is eating serotonin-rich foods such as bananas, pineapples, walnuts, pecans, avocados, or hickory nuts or is taking certain medications cough syrup containing guaifenesin, acetaminophen, salicylates, serotonin reuptake inhibitors, or 1-dopa. The normal range in daily urinary 5-HIAA excretion is 2-8 mgd. Most physicians use only the urinary 5-HIAA excretion rate; however, plasma and platelet serotonin levels, if available, may provide additional information. Platelet serotonin levels are more sensitive than urinary 5-HIAA but are not generally available. Because patients with foregut carcinoids may produce an atypical carcinoid syndrome, if this syndrome is suspected and the urinary 5-HIAA is minimally elevated or normal, other urinary metabolites of tryptophan, such as 5-HTP and 5-HT, should be measured. Serum chromogranin A levels are elevated in 56-100 of patients with carcinoid tumors, and the level correlates with tumor bulk. Serum chromogranin A levels are not specific for carcinoid tumors. Plasma neuron-specific enolase levels are also used as a marker of carcinoid tumors but are less sensitive than chromogranin A, being increased in only 17-47 of patients. 