5-Hydroxyindoleacetic acid (5HIAA) test
The 5-Hydroxyindoleacetic acid (5HIAA) test measures the levels of a metabolite produced when the body breaks down serotonin. This test is primarily utilized to diagnose and monitor carcinoid tumors, which release excess serotonin, and can also indicate conditions such as cystic fibrosis, depression, and migraines. To prepare for the test, patients must avoid certain foods, including fruits and nuts, as well as various medications that could interfere with the results. Typically, a 24-hour urine sample is collected, though random samples may also be used.
Elevated 5HIAA levels may suggest the presence of a carcinoid tumor, prompting further imaging tests like MRI or CT scans. However, it is important to note that normal 5HIAA levels do not rule out tumors, and elevated levels can occur without tumor presence. As such, the test results should be interpreted in conjunction with clinical symptoms and other diagnostic procedures. Overall, the 5HIAA test is a valuable tool for healthcare providers in diagnosing and managing specific health conditions.
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5-Hydroxyindoleacetic acid (5HIAA) test
ALSO KNOWN AS: HIAA test, serotonin metabolite test
DEFINITION: 5-Hydroxyindoleacetic acid (5HIAA) is the compound that results when the body breaks down (metabolizes) the hormone serotonin.
Cancers diagnosed: Endocrine system and carcinoid tumors
Why performed: Carcinoid tumors release large amounts of serotonin, so doctors look for its metabolite, 5HIAA, in the urine. This test helps diagnose and monitor the treatment of these types of tumors. It also indicates cystic fibrosis, depression, and migraines. Patients who need this test may be experiencing diarrhea, nausea, vomiting, low blood pressure, unexplained weight loss, irregular heartbeat, or wheezing.
Patient preparation: Patients are instructed to avoid fruits and nuts in general and, specifically, avocados, bananas, eggplant, kiwis, pineapple and pineapple juice, plums, tomatoes and all tomato products, and walnuts for at least three days before and during this test. These foods can interfere with the test results. In addition, the drugs caffeine, nicotine, acetaminophen (Tylenol), aspirin, cough medicine, diazepam (Valium), ephedrine, heparin, imipramine, isoniazid, levodopa, monoamine oxidase inhibitors, methyldopa, phenobarbitol, and tricyclic antidepressants, as well as herbal and over-the-counter medicines, can interfere with test results.
Steps of the procedure: Generally, a patient provides a twenty-four-hour urine sample, which involves collecting and refrigerating all urine excreted over twenty-four hours. If it is impossible to collect all urine over twenty-four hours, random urine samples may be collected. Still, this type of test is less accurate because 5HIAA levels can vary throughout the day.
After the procedure: If the test is used as a diagnostic tool and levels of 5HIAA are elevated, leading to a suspicion of a carcinoid tumor, then further tests, such as magnetic resonance imaging (MRI) or a computed tomography (CT) scan, may be performed to determine the existence and location of the tumor. If the test is used as a monitoring tool, then decreasing levels of 5HIAA will indicate that a tumor is responding to treatment, whereas increasing levels indicate that treatment has not been successful.
Risks: 5HIAA levels may be normal even when carcinoid tumors are present. Conversely, 5HIAA levels may be elevated, though no tumors exist.
Results: Because results vary widely and false negative and false positive results are common, this test does not definitively diagnose carcinoid tumors. The results should be used along with symptoms to determine what further testing is necessary for a diagnosis. As a monitoring tool, the results of this test are used to determine the level of treatment success. In combination with the 5HIAA test, medical providers may order a blood test to confirm the presence of chromogranin A, a tumor marker protein. A liver scan is also commonly performed after the 5HIAA test.
Bibliography
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Feldman J. M., and E. M. Lee. "Serotonin Content of Foods: Effect on Urinary Excretion of 5-Hydroxyindoleacetic Acid." American Journal Clinical Nutrition, vol. 42, no. 4, 1985, pp. 639–43. doi:10.1093/ajcn/42.4.639.
Fila, Michal, et al. “Urine 5-Hydroxyindoleacetic Acid Negatively Correlates with Migraine Occurrence and Characteristics in the Interictal Phase of Episodic Migraine.” International Journal of Molecular Sciences, vol. 25, no. 10, 2024. MDPI, doi.org/10.3390/ijms25105471.
“5-HIAA.” MedlinePlus, 15 Aug. 2022, medlineplus.gov/ency/article/003612.htm. Accessed 20 June 2024.
Parker, James N., Philip M. Parker, and Parker, Philip M. The Official Patient's Sourcebook on Gastrointestinal Carcinoid Tumors. ICON, 2007.