Q. Thank you for the excellent, clear article (the November 2013 issue’s “What’s in a Test,” on page 21, infographic available at TheHorse.com/32655) that addressed blood tests in sick horses. But what about testing in a presumed healthy horse? What is the advisability of doing routine blood tests to help get an indication of a horse’s health as part of a prepurchase exam? And what is the advisability of doing annual routine blood tests on a seemingly well horse during an annual examination, similar to annual tests done for humans?

Leslie Raulin, Jefferson, Md.

A. It is not unreasonable to do routine blood tests on a horse as part of the annual or prepurchase examination. Blood testing is a simple way to assess your horse’s overall state of health, as well as a way to identify early warning signals that could precede the development of serious diseases. Even if the results are normal it is always useful to have baseline values to compare from year to year or to refer to if there is a change later.

Because variabilities exist between laboratories, the one that performs the test should compare the results with normal ranges established for horses of a similar age at that lab. Your veterinarian will interpret the blood work based on the clinical status of the horse. Routine testing usually includes a complete blood count (CBC) and a chemistry profile, as described in the article you mentioned. In older horses additional blood tests should be performed to screen for equine met