Carcinoid tumor is diagnosed by -

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 mg/d.* 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.