Test Catalog

Test Id : 7AC4

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7AC4, Bile Acid Synthesis, Serum

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Overview

Test Catalog

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

Screening for bile acid malabsorption in patients with irritable bowel syndrome with diarrhea

Highlights

This test should be used for screening for bile acid malabsorption, a condition in which excess bile acids are found in the stool that is one cause of chronic diarrhea.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

For more information see Ordering Guide: Bile Acid-Associated Tests.

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.

Yes

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

7AC4, Bile Acid Synthesis, S

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

7(a)-Hydroxy-cholesten-3-one

7alphaC4

7C4

7AC4

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

For more information see Ordering Guide: Bile Acid-Associated Tests.

Specimen Type
Describes the specimen type validated for testing

Serum

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

Patient Preparation:

1. Patient must fast for at least 12 hours prior to collection; fasting morning specimen is preferred.

2. Patient should not be taking bile acid sequestrants for 24 hours prior to collection or statins for 5 days prior to collection.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Centrifuge and aliquot 1 mL of serum into plastic vial.

2. Send specimen frozen.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Forms

If not ordering electronically, complete, print, and send Gastroenterology and Hepatology Test Request (T728) with the specimen

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

0.5 mL

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

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

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
Serum Frozen (preferred) 90 days
Refrigerated 72 hours
Ambient 24 hours

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

Screening for bile acid malabsorption in patients with irritable bowel syndrome with diarrhea

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

For more information see Ordering Guide: Bile Acid-Associated Tests.

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

Bile acids are synthesized from cholesterol in the liver and released into the digestive tract where they function to emulsify dietary fats and facilitate lipid absorption in the small intestine. More than 95% of bile acids are then reabsorbed primarily by active uptake in the distal ileum, while less than 5% are excreted in stool. The synthesis of bile acids in the liver is regulated by a negative feedback mechanism from the bile acids reabsorbed from the intestine. 7 Alpha-hydroxy-4-cholesten-3-one (7aC4) is an intermediate in the biosynthesis pathway of cholesterol to bile acids. The concentration of 7aC4 in serum is a surrogate for the amount of bile acid synthesis in the liver. There is some diurnal variation in 7aC4 serum concentrations, so measurement should be performed on a fasting morning sample.

 

Patients with increased bile acid in their stool suffer from chronic diarrhea termed bile acid diarrhea (BAD). Approximately 10% to 33% of patients with irritable bowel syndrome with diarrhea have BAD. Additionally, BAD has been identified as a contributor of diarrhea in other conditions such as irritable bowel disease (IBD), Celiac disease, microscopic colitis, and neuroendocrine tumors.(1) Identifying patients with BAD can be done by measuring total and fractionated bile acids in stool. The increased bile acids in feces can be caused by an inability to reabsorb bile acids in the terminal ileum (bile acid malabsorption: BAM). If the intestinal reabsorption if BA is decreased, this leads to increase synthesis of bile acids in the liver. Recent studies have shown that serum concentrations of 7aC4 are elevated in patients with BAD. Several intestinal diseases or functional abnormalities can lead to BAD.

 

The definitive test in the United States for BAD is the 48-hour stool bile acids test (BA48F / Bile Acids, Bowel Dysfunction, 48 Hour, Feces). However, given the challenge of a 48-hour specimen collection, a random stool collection can be used in combination with the results from serum 7aC4 testing. From a random stool collection, only the percentage of primary bile acids can be reported. Internal studies have shown that a combination of serum 7aC4 result above 52.5 ng/mL and primary fecal bile acid result above 10% is 66% sensitive and 95% specific for BAD.(2)

 

Identification of these patients can influence treatment decisions that could include the use of bile acid sequestrants. Conversely, patients with irritable bowel syndrome with constipation may have lower circulating 7aC4 as compared to healthy individuals.

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 =18 years: 2.5-63.2 ng/mL

Reference values have not been established for patients who are <18 years of age.

Interpretation
Provides information to assist in interpretation of the test results

In patients with irritable bowel syndrome with diarrhea, elevated 7alpha-hydroxy-4-cholesten-3-one (7aC4) is consistent with bile acid diarrhea (BAD). A result of 17.6 ng/mL or greater is 83% sensitive and 53% specific for BAD. In these cases, a confirmatory 48-hour fecal bile acid test could be considered. A result above 52.5 ng/mL is 40% sensitive and 85% specific for BAD.

 

Interpretation of 7aC4 results in patients with chronic diarrhea (bile acid malabsorption: BAM):

Below 17.6

17.6 or above

Above 52.5

BAM unlikely,

consider other conditions

BAM indeterminate,

consider confirmatory fecal bile acids test or

trial of bile acid sequestrant

BAM likely,

consider bile acid sequestrant therapy

 

Serum 7aC4 can be used in combination with a random (single collection) stool bile acid assessment for increased sensitivity and specificity for BAM detection. See BAMRP / Bile Acids Malborption Panel, Serum and Feces.

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

Testing should not be performed on individuals with liver disease or dysfunction.

Supportive Data

In an internal study of 55 patients with irritable bowel syndrome with diarrhea, a fasting serum 7 alpha-hydroxy-4-cholesten-3-one (7aC4) result of 17.6 ng/mL or above was 83% sensitive and 53% specific for identifying patients with elevated fecal bile acids (eg, patient with bile acid diarrhea).(3) In another study, a result above 52.5 ng/mL resulted in 40% sensitivity and 85% specificity for BAD.(4)

Additional internal studies have shown that a combination of serum 7aC4 above 52.5 ng/mL and primary fecal bile acids above 10% is 66% sensitive and 95% specific for BAD.(2)

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

1. Vijayvargiya P, Gonzalez Izundegui D, Calderon G, et al: Increased fecal bile acid excretion in a significant subset of patients with other inflammatory diarrheal diseases. Dig Dis Sci. 2022 Jun;67(6):2413-2419

2. Camilleri M, Nadeau A, Tremaine WJ, et al: Measurement of serum 7 alpha-hydroxy-4-cholesten-3-one (or 7AC4), a surrogate test for bile acid malabsorption in health, ileal disease and irritable bowel syndrome using liquid chromatography-tandem mass spectrometry. Neurogastroenterol Motil. 2009;21(7):734-743

3. Vijayvargiya P, Camilleri M, Carlson P, et al: Performance characteristics of serum C4 and FGF19 measurements to exclude the diagnosis of bile acid diarrhoea in IBS-diarrhoea and functional diarrhoea. Aliment Pharmacol Ther. 2017;46(6):581-588. doi: 10.1111/apt.14214

4. Vijayvargiya P, Camilleri M, Shin A, et al: Methods for diagnosis of bile acid malabsorption in clinical practice. Clin Gastroenterol Hepatol. 2013;11(10):1232-1239

5. Vijayvargiya P, Camilleri M, Taylor A, et al: Combined fasting serum C4 and primary bile acids from a single stool sample to diagnose bile acid diarrhea. Gastroenterology. 2020 Nov;159(5):1952-1954.e23.

6. Wong BS, Camilleri M, Carlson P, et al: Increased bile acid biosynthesis is associated with irritable bowel syndrome with diarrhea. Clin Gastroenterol Hepatol. 2012 Sep;10(9):1009-1015.e3

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

7 Alpha-hydroxy-cholesten-3-one (7aC4) is extracted from the sample. After addition of a deuterium-labeled 7aC4 internal standard, 7aC4 is measured by liquid chromatography tandem mass spectrometry. (Donato LJ, Lueke A, Kenyon SM, Meeusen JW, Camilleri M: Description of analytical method and clinical utility of measuring serum 7-alpha-hydroxy-4-cholesten-3-one (7aC4) by mass spectrometry. Clin Biochem. 2018;52:106-111)

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

No

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, Thursday

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.

5 days

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

14 days

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

Rochester

Fees
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.

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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. It 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.

82542

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
7AC4 7AC4, Bile Acid Synthesis, S 94866-1
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.
65504 7AC4, Bile Acid Synthesis, S 94866-1

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 | PHP Pdf | CMS 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