Bile Acid Testing and Protein C
answered by Dr. Karen Tobias
Is it necessary to fast a dog for bile acid testing?
When we look
at the literature, 100% of the fed samples and 95% of the fasting samples are
abnormal in dogs with shunts. So, the fed sample is more important.
However, we also tend to look at the total number. For instance, UTCVM
normals are <10 fasted and <15 fed. If we got a 12 on the fasted sample,
most of of would not be so excited. Same for if we got a 17after a fed
Feeding makes the gallbladder contract, primarily because of fats in the diet that stimulate hormone release. Since 20% of dogs have a normal gallbladder contraction in the middle of the night, their values will be reversed (fasting higher than fed). The fasted sample will be higher because the dog's gallbladder contracted (just like it would if the dog was fed), and therefore the fasted sample is actually a "fed sample". That will make interpretation of results difficult. You can't assume that an animal that has a "fed" sample of 15 would have a fasted sample that was lower, because that may not be the case in 20% of the animals.
Here's the bottom line: If you get a fasting sample that is very high, there is no reason to run a second test (fed sample) because we already know the dog has liver problems. If you get a fed sample that is very high, there is no reason to run two tests (a fasting and a fed) because we already know the dog has liver problems. If you get a single sample that is normal, you cannot be 100% sure that it is correct (only 80%).
As to Protein C, the test is not specific for shunts or MVD. It can be abnormally low with any liver disease, and with some infections and inflammation as well. Results of the test must be combined with other information from the dog. Since we are now seeing a lot of shunt dogs with normal protein, albumin, cholesterol, and BUN and no apparent clinical signs (except that the dogs are quiet or small or have ratty hair coats), we can't depend on those other factors to help us differentiate shunt from MVD. Bile acids will not differentiate them either. At this point, there is no perfect blood test. I hope Dr. Center's genetic test will be successful so that we can try to clear this condition out of the breed.
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