The primary biochemical marker for midgut carcinoid tumors, and less often, foregut tumors.
It is the metabolite of serotonin, that is broken down by the liver and is excreted by the kidneys.
It is the preferred initial laboratory test for carcinoid syndrome.
Elevated levels are associated with carcinoid syndrome of flushing, diarrhea, and carcinoid heart disease.
Test is used to diagnose and monitor carcinoid syndrome and is the measurement of 5-hydroxyindolacetic acid, a serotonin metabolite that can be measured in the urine.
24 hour urinary levels as a measure of carcinoid tumor activity is preferred over plasma serotonin, which is variable over a 24-hour period.
Elevated levels associated with shorter survival than those with normal levels.
The degree of elevation of urinary 5-HIAA levels correlates with the severity of the carcinoid syndrome.
Elevated levels associated with the development of cardiac valvular disease, presumably related to its relationship with serotonin.
The highest levels or failed with patients with carcinoid induced heart failure.
This biochemical marker has a specificity of approximately 88% (Modlin IM).
Serotonin rich foods such as bananas, avocados, plums, egg plant, tomatoes, plantains, pineapples and walnuts must be avoided during specimen collection as they may impair the accuracy of the test.
Such foods should not be ingested within 72 hours before testing.
Tryptophan containing supplements can cause an increase in urinary 5HIAA through an increased conversion of tryptophan to serotonin.