What are the other Names for this Test? (Equivalent Terms)
- 5-Hydroxyindole Acetic Acid Test
- 5-Hydroxyindoleacetic Acid (5-HIAA) Test
- Serotonin Metabolite Test
What is 5-HIAA Test? (Background Information)
- Carcinoid tumors are a type of endocrine tumors that are characterized by their secretion of large amounts of the hormone serotonin
- The amino acid tryptophan is converted by these endocrine tumors to serotonin in large quantities. When this overproduced serotonin reaches the tissues (such as in the lungs or gastrointestinal region), they produce a set of debilitating symptoms that are known as carcinoid syndrome
- The liver has enzymes that neutralize most excess serotonin hormone produced, by breaking it down into metabolites (products of metabolism). This controls the level of serotonin in blood and prevents it from reaching the tissues in high levels
- One of the most important byproduct produced during breakdown of serotonin is called 5-Hydroxyindoleacetic Acid (5-HIAA)
- 5-HIAA Test: By measuring the urinary 5-HIAA quantity, one can diagnose the symptoms caused by carcinoid syndrome. This helps the healthcare provider initiate action, to locate the carcinoid tumors and/or propose a treatment course
What are the Clinical Indications for performing the 5-HIAA Test?
Individuals with the following set of non-specific symptoms that may point to carcinoid tumors, may be prescribed 5-HIAA testing. These include:
- Flushing (sudden reddening around the face and neck region) with no sweating , increased heart beat rate / palpitations
- Heart diseases due to heart valve problems
- Nocturnal ( night time) diarrhea, vomiting, and nausea
- Difficulty in breathing, persistent cough
- Abdominal pain
Additionally, those undergoing treatment for carcinoid tumors, have to be regularly tested and monitored. This is performed by detecting the urinary levels of 5-hydroxyindoleacetic acid, in such individuals.
How is the Specimen Collected for 5-HIAA Test?
Sample required: Urine, which may be a random urine sample, or 24-hours urine sample.
Procedure for collecting 24-hour urine sample:
- The first urine sample, after waking up in the morning, is discarded. The time is noted down, and this marks the beginning of a 24-hour collection period
- All urine, over the next 24-hour period is collected in a large container (normally supplied by the healthcare provider)
- Do not contaminate the large container. Use a small container to collect urine, each time. Transfer this into the large container
- Use ice to keep the container at very low temperature (else refrigerate the container and contents)
- Just before the end of the 24-hour collection period, empty the bladder one last time, to collect the final urine sample
- Keep the 24-hour urine sample free of any contaminants or foreign matter, like toilet paper, stool, menstrual blood, pubic hair, etc.
Preparation required: Starting 2-3 days, prior to and on the day of sample collection, is very important. The following have to be avoided, in order to prevent them from interfering with the test results:
- Certain medications, such as acetaminophen, aspirin, ephedrine, heparin, isoniazid, and many others
- The following fruits and vegetables: avocado, banana, eggplant, hickory nuts, kiwi, pecans, pineapple, plum, tomato, walnuts, etc.
- In all cases, always consult your healthcare provider before discontinuing (temporarily) any medication
What is the Significance of the 5-HIAA Test Result?
- Abnormally elevated levels of 5-HIAA in the urine sample (24-hr) combined with the carcinoid syndrome symptoms can indicate the presence of a carcinoid tumor
- However, in order to confirm the biochemical test results and/or isolate the tumor, imaging scans are normally performed. This may be followed with a biopsy of the affected tumor
- For those individuals already diagnosed with carcinoid tumors, such tests help in evaluating the treatment effectiveness
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
- In the early stages, carcinoid tumors are extremely difficult to diagnose due the lack of any significant symptoms. Many a times they are discovered accidently, or only after the carcinoid syndrome symptoms manifest
- Carcinoid tumors occur mostly in the gastrointestinal tract (65% of the times) and in the lungs and airways (25% of the times)
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.