Laboratory Test Name for Bile Acids
The test is called "serum bile acids" or "total serum bile acids" (also abbreviated as SBA or TBA), and can be ordered as either a fasting or random sample depending on the clinical context. 1
Test Nomenclature and Ordering
The most commonly used term on laboratory panels is "total serum bile acids" or "serum bile acids", which measures the aggregate level of all bile acid species in the blood 1
Some laboratories may list it as "total bile acid level" or use the abbreviation "TBA" (total bile acids) 2, 3
The test may also appear as "fasting total serum bile acid" (FTBA) if specifically ordered as a fasting sample 3, 4
Available Testing Methods
Two main assay types are available, and clinicians should verify which method their laboratory uses: 1
Enzymatic assay: Turnaround time of 4 hours to 4 days, available at some hospital laboratories and specialty labs, measures only total bile acids 1
Mass spectrometry/liquid chromatography: Turnaround time of 4-14 days, performed by specialty laboratories, can provide fractionated levels (cholic acid, chenodeoxycholic acid, deoxycholic acid) but the fractionated values have limited clinical utility 1
Fasting vs. Random Sampling
Random (non-fasting) bile acid levels are acceptable for diagnosis and more convenient for patients and practitioners 1
The differences between random and fasting results are small, and most published studies on intrahepatic cholestasis of pregnancy used random samples 1
Fasting samples may be preferred for certain contexts like serum C4 testing (7α-hydroxy-4-cholesten-3-one), which shows diurnal and postprandial variation 5
Alternative and Specialized Tests
For bile acid diarrhea specifically, alternative tests include: 1, 6
48-hour stool bile acid collection (documents increased fecal bile acids) 1
Serum fibroblast growth factor 19 (measures defective feedback of bile acid synthesis) 1
Serum C4 (7α-hydroxy-4-cholesten-3-one, a measure of bile acid synthesis) 1, 6
SeHCAT scan (preferred test where available, not available in North America) 1, 6