7AC4, Bile Acid Synthesis, Serum
Use
This test is used for screening for bile acid malabsorption—a condition in which excess bile acids are found in the stool and may contribute to chronic diarrhea. Serum 7α-hydroxy-4-cholesten-3-one (7aC4) is a surrogate marker for bile acid synthesis in the liver and is elevated in patients with bile acid diarrhea, particularly those with irritable bowel syndrome with diarrhea (IBS‑D). It helps to identify patients who may benefit from treatment with bile acid sequestrants, and its combination with a stool test can improve diagnostic accuracy.
Special Instructions
For non-electronic orders, the Gastroenterology and Hepatology Test Request (T728) form must accompany the specimen. Additional ordering guidance is available in the Ordering Guide: Bile Acid‑Associated Tests.
Limitations
There is diurnal variation in 7aC4 serum concentrations, so fasting morning samples are preferred. Elevated 7aC4 is consistent with bile acid diarrhea (BAD), but confirmatory testing such as a 48‑hour fecal bile acids test may be indicated, especially when results are in intermediate ranges. Interpretation thresholds include ≥17.6 ng/mL (83% sensitivity, 53% specificity) and >52.5 ng/mL (40% sensitivity, 85% specificity). Performance may vary in certain conditions and patient populations.
New York Approved
Methodology
Mass Spectrometry (LC‑MS/MS)
Biomarkers
LOINC Codes
- 94866-1
- 94866-1
Result Turnaround Time
5 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.5 mL
Container
Serum gel (preferred); red top (acceptable); plastic vial for submission
Collection Instructions
Fasting: 12 hours required; fasting morning specimen is preferred. Patient should not be taking bile acid sequestrants for 24 h or statins for 5 days prior to collection. Centrifuge and aliquot 1 mL of serum into a plastic vial. Send specimen frozen.
Patient Preparation
Fasting 12 h; avoid bile acid sequestrants 24 h and statins 5 days prior
Causes for Rejection
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 24 hours |
| Refrigerated | 72 hours |
| Frozen | 90 days |