To help diagnose and monitor treatment for a carcinoid tumor that produces serotonin
5-HIAA
When you have symptoms suggestive of a carcinoid tumor, such as flushing, abdominal pain, diarrhea, and/or wheezing; at intervals following treatment
A 24-hour urine sample; rarely, a random urine sample or a blood sample drawn from a vein
You may be instructed to avoid certain foods and medications prior to this test. (For more details, see the "What is being tested?" section below.)
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How is the test used?
The 5-hydroxyindoleacetic acid (5-HIAA) test is used to help diagnose and monitor carcinoid tumors. It may be ordered by itself or along with a blood serotonin and/or chromogranin A level.
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When is it ordered?
This test is primarily ordered when you have signs and symptoms suggestive of a carcinoid tumor.
Some examples include:
- Flushing of the face and neck (appearance of deep red color, usually with sudden onset)
- Diarrhea, abdominal pain, nausea, vomiting
- Rapid heart rate
- Wheezing, coughing, difficulty breathing
This test may also be ordered at intervals when monitoring the effectiveness of treatment for a carcinoid tumor. -
What does the test result mean?
A significantly increased level of 5-HIAA when you have carcinoid syndrome symptoms is suggestive but not diagnostic of a carcinoid tumor. In order to diagnose the condition, the tumor itself must be located, biopsied, and examined by a pathologist. Your healthcare practitioner will frequently follow an abnormal test result with an order for an imaging scan to help locate any tumor(s) that may be present.
You may still have a carcinoid tumor even if your 5-HIAA level is normal. Some carcinoid tumors do not produce serotonin or only produce it intermittently.
If you have no symptoms and normal levels of 5-HIAA, it is unlikely you have a carcinoid tumor that produces serotonin.
If you are being monitored following treatment for carcinoid tumor, decreasing levels of 5-HIAA indicate a response to treatment, while increased or rising levels indicate that treatment has not been successful.
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Is there anything else I should know?
There are a variety of drugs that can affect the 5-HIAA test:
- Medications that can increase 5-HIAA include acetaminophen, caffeine, ephedrine, diazepam (Valium®), fluorouracil, glyceryl guaiacolate (an ingredient found in some cough medicines), melphalan (Alkeran®), mephenesin, methamphetamine (Desoxyn), methocarbamol (Robaxin®), naproxen, nicotine, phenacetin, phenmetrazine, phenobarbital, phentolamine, rauwolfia, and reserpine.
- Medications that can decrease 5-HIAA include aspirin, chlorpromazine (Thorazine), corticotropin, dihydroxyphenylacetic acid, ethyl alcohol, gentisic acid, homogentisic acid, hydrazine derivatives, imipramine(Tofranil®), isocarboxazid (Marplan), levodopa, MAO inhibitors, heparin, isoniazid, methenamine, methyldopa(Aldomet®), perchlorperazine, phenothiazines (Compazine®), promazine, promethazine (Mepergan®) and tricyclic antidepressants.
You should talk to your healthcare provider before decreasing or discontinuing any medications. -
Why do I have to collect my urine for 24 hours?
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Will my results be accurate if I must continue to take my medication?
If the drug is one that can increase or decrease the amount of serotonin and 5-HIAA, then your results may be affected. However, it is up to your healthcare provider and you to decide whether or not your medication can be safely stopped prior to and during the test collection. If your drugs must be taken, then your healthcare practitioner will interpret the test results with this in mind.
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Are some people at a higher risk for developing a carcinoid tumor?
Anyone at any age can develop a carcinoid tumor but, according to the American Cancer Society, the average age at diagnosis is usually in the early 60s. People with a family history of multiple endocrine neoplasia (MEN1), a genetic condition that increases a person's risk of developing tumors in the endocrine system glands, may be at higher risk for developing a carcinoid tumor.