Test Catalog

Test Id : HIAAP

5-Hydroxyindoleacetic Acid, Plasma

Useful For
Suggests clinical disorders or settings where the test may be helpful

Biochemical diagnosis and monitoring of intestinal carcinoid syndrome using a plasma specimen

Method Name
A short description of the method used to perform the test

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.


Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

5-Hydroxyindoleacetic Acid, P

Lists additional common names for a test, as an aid in searching

5-HIAA (5-Hydroxyindolacetic Acid)

5-OH-Indoleacetic Acid

Carcinoid Syndrome

NET (Neuroendocrine Tumor)

HIAA (Hydroxyindoleacetic Acid)

Serotonin Metabolite

Specimen Type
Describes the specimen type validated for testing


Ordering Guidance

This test quantifies 5-hydroxyindoleacetic acid in plasma specimens and is comparable to testing on 24-hour and random urine specimens for the diagnosis and monitoring of intestinal carcinoid syndrome.

Necessary Information

Patient’s age is required.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Patient Preparation:

1. Some medications could interfere with test results. The ordering provider should decide if any medications should be stopped and when they should be restarted. If clinically feasible, discontinue the following medications at least 24 hours prior to specimen collection:

-Acetaminophen (Tylenol or generic versions)

-Tryptophan containing supplements.

2. For 24 hours prior to the collection, the patient should:

Limit the following to one serving per day:



-Caffeinated beverages or foods

Abstain from the following:

-Nuts, especially walnuts. Plasma 5-hydroxyindoleacetic acid levels revert to baseline levels when walnuts are ingested after other foods.


Collection Container/Tube:

Preferred: Green top (sodium heparin)

Acceptable: Lavender top (EDTA)

Submission Container/Tube: Plastic vial

Specimen Volume: 0.5 mL

Collection Instructions:

1. Centrifuge at 4 degrees C.

2. Aliquot plasma into plastic vial.

3. Send plasma frozen.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

0.2 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis OK
Thawing** Cold OK; Warm reject
Gross lipemia OK
Gross icterus OK

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

Specimen Type Temperature Time Special Container
Plasma Frozen (preferred) 60 days
Refrigerated 72 hours

Useful For
Suggests clinical disorders or settings where the test may be helpful

Biochemical diagnosis and monitoring of intestinal carcinoid syndrome using a plasma specimen

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Intestinal carcinoid and neuroendocrine tumors can produce excess amounts of serotonin and its degradation product, 5-hydroxyindoleacetic acid (5-HIAA). Determination of 5-HIAA in urine or plasma is used to diagnose and monitor patients with carcinoid syndrome.


Carcinoid syndrome is characterized by a constellation of hormonal symptoms such as abdominal pain, increased bowel movements, episodic facial flushing, bronchoconstriction, venous telangiectasia, niacin deficiency-related symptoms, and long-term complications, such as mesenteric fibrosis and carcinoid heart disease.(1)


Measurement of 5-HIAA in a plasma specimen can diagnose carcinoid disease and produces comparable results to urinary 5-HIAA testing.

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

< or =6 months: < or =130 ng/mL

>6 months: < or =30 ng/mL

Provides information to assist in interpretation of the test results

If pharmacological and dietary artifacts have been ruled out, an elevated concentration of 5-hydroxyindoleacetic acid is a probable indicator of the presence of a serotonin-producing tumor.

Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Intake of food with a high content of serotonin (avocados, dates, eggplant, all fruit [including bananas, cantaloupe, grapefruit, kiwifruit, melons, pineapple, plantains, plums], all nuts [including walnuts, hickory nuts, butternuts, pecans], and tomatoes and tomato products) within 24 hours of the plasma collection could result in falsely elevated 5-hydroxyindoleacetic acid (5-HIAA) excretion.


Numerous drugs affect the excretion of 5-HIAA by different mechanisms, including increased serotonin synthesis, metabolism, and release and inhibition of uptake. The following medications can interfere with 5-HIAA results.

-Acetaminophen (Tylenol or generic versions)

-Tryptophan containing supplements

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Oleinikov K, Avniel-Polak S, Gross DJ, Grozinsky-Glasberg S. Carcinoid syndrome: Updates and review of current therapy. Curr Treat Options Oncol. 2019 Jul 9;20(9):70. doi: 10.1007/s11864-019-0671-0

2. Adaway JE, Dobson R, Walsh J, et al. Serum and plasma 5-hydroxyindoleacetic acid as an alternative to 24-h urine 5-hydroxyindoleacetic acid measurement. Ann Clin Biochem. 2016 Sep;53(Pt 5):554-560. doi: 10.1177/0004563215613109

3. Tohmola N, Johansson A, Sane T, et al: Transient elevation of serum 5-HIAA by dietary serotonin and distribution of 5-HIAA in serum protein fractions. Ann Clin Biochem. 2015 Jul;52(Pt 4):428-33. doi: 10.1177/0004563214554842

4. Tellez MR, Mamikunian G, O'Dorisio TM, Vinik AI, Woltering EA. A single fasting plasma 5-HIAA value correlates with 24-hour urinary 5-HIAA values and other biomarkers in midgut neuroendocrine tumors (NETs). Pancreas. 2013 Apr;42(3):405-10. doi: 10.1097/MPA.0b013e318271c0d5

Method Description
Describes how the test is performed and provides a method-specific reference

Plasma is mixed with deuterium labeled hydroxyindoleacetic acid (HIAA) as internal standard in acetonitrile. After centrifugation and filtration, the sample is reconstituted in mobile phase. Liquid chromatography tandem mass spectrometry is performed by injecting the reconstituted specimen onto a reverse phase high-performance liquid chromatography column. HIAA is quantitated using the stable isotope-labeled internal standard from calibration over a concentration range of 0 to 1000 ng/mL.(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday, Wednesday, Friday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

3 to 6 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 month

Performing Laboratory Location
Indicates the location of the laboratory that performs the test


Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.


LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
HIAAP 5-Hydroxyindoleacetic Acid, P 1693-1
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
619735 5-Hydroxyindoleacetic Acid, P 1693-1

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports

Test Update Resources

Change Type Effective Date
New Test 2023-04-25