<prompt> Best test for diagnosis of Carcinoid tumor:24 hour urinary 5H.I.A.A24 hour catecholamines24 hour vaniylmandelic acid levels24 hour metanephrine levels  <response>: Ans. a 24 hour urinary 5H.I.A.ARef: Harrison 19th ed. 1564-65 5-HLAA is the major urinary metabolite of serotonin, a ubiquitous bioactive amine. Serotonin, and consequently 5-HLAA, are produced in excess by most carcinoid tumors, especially those producing the carcinoid syndrome of flushing, hepatomegaly, diarrhea, bronchospasm, and heart disease. 