Top 10 Blood Tests
Learn what blood tests are most meaningful to your veterinarian—and what basic lab work will (or won’t) tell you about your horse’s health.
Learn what basic lab work can tell you and your veterinarian about your horse’s health.
Your horse is under the weather, and your vet doesn’t know what’s wrong. “We should probably run some basic lab work,” he explains. “Maybe that’ll help us figure out what to do.” Just about every horse owner has given the green light for “basic lab work” that includes a complete blood count and chemistry panel. I’ll unravel some of the mysteries about basic blood work. I’ll start by explaining the most common reasons I suggest blood work and what factors I consider when interpreting the results. Then I’ll tell you about the 10 tests I always look at first—including what they might mean and how they relate to other tests. You’ll learn why blood work is an important tool in your vet’s tool box, and how to make the most of the results.
Your horse’s blood is his basic internal transport system. It carries oxygen from his lungs to his other organs, delivers nutrients from his intestines, transmits proteins or other specialized cells to places where they’re needed, and carries waste materials away for elimination. When your horse is healthy, the substances in the blood typically stay within a certain range. When something’s wrong, one type of cell or substance may go out of whack. Knowing this provides information to help identify the problem.
Hundreds of tests can be performed on a sample of blood, ranging from a simple count of red blood cells to a test for hormone levels that might indicate a specific disease. I’ll limit my focus to the basics, made up of a complete blood count (or CBC) and chemistry panel.
A CBC provides information about the number and characteristics of red and white blood cells circulating in your horse’s system, as well as a breakdown of the different types of white blood cells. The chemistry panel consists of a number of tests that help evaluate the health and function of internal organs, as well as measurement of proteins that are involved with inf lammation. Your vet will most likely suggest basic blood work for one of the following five reasons.
Your horse is losing weight. The most common reasons for weight loss include parasites, dental problems, and poor nutrition. If your vet determines that these basic issues aren’t the cause and he finds nothing unusual on a physical examination, he’ll suggest blood work that might identify more serious causes for your horse’s weight loss, such as liver or kidney disease.
Your horse has a fever. A fever is usually caused by one of three things: an inflammatory problem, a viral infection, or a bacterial infection. Blood work can help your vet determine the likelihood of bacterial involvement, and help him decide whether to treat with antibiotics. It can also help your vet evaluate the severity of your horse’s problem.
Your horse is off his feed with no other signs. If your horse stops eating yet shows no other symptoms, and your vet can’t find anything amiss on a physical exam, blood work might help provide an answer—whether it’s a low-grade infection, source of inflammation, or organ dysfunction.
Your horse just doesn’t seem right. Your horse might be eating and passing manure normally, but something just “seems off.” Blood work can give you peace of mind that
nothing is wrong—or it might give you a clue about a problem brewing.
Routine screening. Routine blood work establishes a baseline for comparison if your horse later becomes ill. This is especially useful for older horses that develop chronic problems that sneak up over time. Routine screening is also valuable for performance horses that experience high levels of stress and often are administered medications such as non-steroidal anti-inflammatories.
Although basic blood work can give you and your vet a lot of information about your horse’s health status, a single lab value or set of tests doesn’t always tell the whole story. To make the most of blood results, make sure your vet has an accurate history about your horse’s condition and is able to do a thorough physical exam. TEST #1: RED BLOOD CELL COUNT RBC What it is: The RBC tells you the total number of red blood cells circulating in your horse’s bloodstream. What it tells you: A low RBC might indicate anemia, while a high RBC is most commonly seen with dehydration. Anemia is most likely in horses secondary to some other chronic disease. Your vet might consider fluid therapy if he notices a very high RBC. Related tests: The RBC is always accompanied by a couple of other tests including the hematocrit (also called “packed-cell volume” or PCV), which indicates the percentage of red blood cells compared with the total volume of blood, and the hemoglobin, which measures of the amount of the protein that carries oxygen within the blood. liver failure), so he’ll look closely at lab values related to organ function.