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Test Code 7AC4 7AC4, Bile Acid Synthesis, Serum


Specimen Required


Patient Preparation:

1. Fasting: 12 hours, required; 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 a plastic vial.

2. Send specimen frozen.


Useful For

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

Method Name

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

Reporting Name

7AC4, Bile Acid Synthesis, S

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Frozen (preferred) 90 days
  Refrigerated  72 hours
  Ambient  24 hours

Reference Values

≥18 years: 2.5-63.2 ng/mL

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

Interpretation

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.

Clinical Reference

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

Day(s) Performed

Monday, Thursday

Report Available

5 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

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

82542

LOINC Code Information

Test ID Test Order Name Order LOINC Value
7AC4 7AC4, Bile Acid Synthesis, S 94866-1

 

Result ID Test Result Name Result LOINC Value
65504 7AC4, Bile Acid Synthesis, S 94866-1

Forms

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

Testing Algorithm

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