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For an explanation of causes of most abnormal blood and urine tests, go here
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TIBC is not as accurate a diagnostic tool in dogs and cats as it has been in humans. But it is still occasionally run as part of an iron panel when your veterinarian is looking for the reason why your pet is anemic.
This test indirectly measures the amount of iron in your pet’s blood that is available to form hemoglobin. That circulating iron is bound to a blood protein called transferrin that is produced mainly in your dog or cat ’s liver. The transferrin+iron complex is eventually carried to your pet’s bone marrow where the iron is used to form the hemoglobin in the new red blood cells that are formed there.
The results of the TIBC test mean the most when they are considered along with the amount of iron free in your pet’s blood serum. In this test, iron is added to a sample of your pet’s blood to see how much the transferrin that is present can absorb. The more iron absorbed, the less the amount of free iron was initially present in your pet’s blood stream. So pets with a high TIBC lack sufficient iron.
Iron deficiency anemia is the most common cause of elevated TIBC and low blood iron levels. The most common cause is probably chronic digestive tract inflammation that allows blood to leave in the pet’s stool and also inhibits the absorption of iron. Many of those conditions in dogs and cats go under the classification of inflammatory bowel disease (IBD).
A true lack of iron in the diet of dogs and cats is quite rare. But immature pets that are bottle fed with un supplemented milk formulas do not receive enough dietary iron. Those puppies and kittens could develop iron deficiency anemia with low blood iron and a high TIBC.
Any chronic blood loss will deplete your pets stores of iron and could increase its TIBC values. Gastrointestinal parasites, like hookworms are very small. Each one absorbs only a small amount of your pets blood. But over time large numbers of these parasites and the intestinal bleeding they cause can also result in iron deficiency anemia (strongyloides parasites can do this as well).
Chronic inflammatory diseases of all kinds can also cause iron deficiency anemia as can various cancers.
Transferrin, the actual compound to which iron binding occurs, is primarily produced by your pet’s liver. So liver disease and things that affect the liver's ability to synthesize transferrin (like portosystemic shunts) can lower its body’s transferrin level causing a low TIBC value in the process. When that situation occurs, the pet’s blood albumen levels should be low as well. Starvation will have the same effect.
Chronic kidney disease can also be a source of leakage of transferrin and albumen into your pet’s urine where it is lost from the body.
TIBC was found to be naturally low in normal racing greyhounds. It was also found to be low in certain tumors of the bone called osteosarcomas.
TIBC can vary from day to day, probably due to fluctuations in your pet’s cortisol levels. If the test is abnormal and no obvious cause is found, rerun the test in a week.