Dr. Center, the developer of the bile acids test, has set the cut off at 25, not 15.
It doesn't sound like your vet did the test properly. You need paired samples around a meal.
Serum bile acids should be collected Before and 2-hours After a meal (this serves as a provocative challenge initiating bile acid release from the gallbladder, intestinal reabsorption, passage into the portal vein to the liver, and rapid liver extraction from the portal blood). The term Postprandial refers to the after meal sample. Dogs DO NOT eed to be fasted for 12-hours to conduct this test. The important issue is to test BEFORE and 2-Hrs after FEEDING to fully evaluate the dogs ability to extract bile acids from the portal circulation. Spilling of portal blood contents into the systemic blood is reflected by finding high Serum Bile Acid values > 25 umol/L in a sample collected from a leg vein or jugular vein.
The sample also needs to be collected properly or the results will be skewed:
The bile acid test is very reliable but the red blood cells MUST be separated from plasma (the clear part of blood) before they are sent to lab for analysis (centrifuged or spun to allow plasma separation from blood cells). Results can be falsely abnormal if the bile acid samples are lipemic (lots of fat IF the fat is not adequately removed by the laboratory analyzing the sample) or if hemolysis (burst red blood cells, makes the plasma red) occurs. The red color interferes with the color of the end point dye in the bile acid test. A clinician can tell if the sample is hemolyzed when they centrifuge the sample to separate the red blood cells from the plasma. If it is hemolyzed they should collect another sample. Drawing blood with a vacutainer needle into a vacutainer (suction of the tube facilitates the collection) may be too traumatic for some red blood cells augmenting hemolysis. Using a syringe and needle or syringe and butterfly needle appears to collect the best samples. After the blood is collected, the needle should be removed from the syringe and the top removed from the vacutainer so that the blood may be gently transferred to the vial. Results of the bile acid test should state if the samples were lipemic or if hemolysis occurred. In this case, the tests should be repeated PSVA and MVD Research Summary