Diagnostic Tests

Anyone who has had a sick dog before knows they often hide their illnesses until they can no longer do so, especially with those they are attached to. Some dogs are more sensitive or vocal than others, but many push through until they become very ill. This is why preventative diagnostic testing is so important. These tests can often reveal issues before our pets show any signs at all. The sooner we know and treat the problem, the better it is for the dog’s health and longevity. Let’s explore and provide some background on what your vet is checking for with these tests.

CBC

CBC (complete blood count) examines the cells in the blood. Red blood cells (RBCs) pick up oxygen in the lungs and deliver it to the tissues. This test determines the proportion of RBCs compared to other components of the blood, the amount of hemoglobin (the protein responsible for carrying oxygen), and the average size of RBCs. All of this helps determine if we have enough RBCs to support our body and how quickly new cells are being produced. White blood cells (WBCs) are counted as a total and in four sub-groups. These cell counts help determine if there is an infection, physiological stress affecting the body’s ability to cope, parasites, inflammation, and immune system dysfunction. A CBC also counts platelets, which are the building blocks used to form a clot to prevent bleeding.

Chemistry

Chemistry refers to a collection of tests of free (non-cellular) metabolites present in the blood. The number of metabolites tested can range from 5 to 30 different values, which can impact cost and result timeline. These tests help determine organ function, evaluate changes over time (trending good/bad when still in the normal range), and can provide an early warning when balance within the body is disturbed. Most organs have multiple values monitored to evaluate function and must be interpreted in context.

Kidney function is monitored using certain values in a chemistry panel. These changes can help your veterinarian determine if the issue is due to increased waste production, poor kidney function, or a blockage preventing urine and excreted metabolites from leaving the body.

Liver function is monitored using multiple values, which can help indicate causes such as issues with the biliary system, liver cell (hepatocyte) dysfunction, or excess metabolites being processed by the liver.

Since the liver and kidneys serve as the body's filters, they often indicate a problem that requires further investigation. This could involve an issue with liver or kidney function or a condition causing increased strain on these filtering organs.

Some tests include values that indicate pancreas or gastrointestinal (GI) health. These tests are typically part of larger panels and may require fasting (the dog should not eat for 12 hours before the sample is collected). Hormone testing can also be included to monitor hormone balance, but it is usually added later in life unless there are signs of an imbalance.

Urinalysis

Urinalysis involves measuring metabolites in urine, assessing urine concentration, and determining the presence of cells, crystals, or bacteria. Urinalysis helps provide needed context to kidney and hormone chemistry results as well as indicate urinary system health. If bacteria are found, a culture and sensitivity test can be conducted to identify the type of bacteria and determine which medications effectively stop growth in the lab. These results assist your veterinarian in selecting the most appropriate antibiotic for the infection.

Fecal

Fecal testing is used to detect parasites and infectious diseases. There are two methods for conducting this test. The first is fecal flotation, which is the traditional and commonly used method. In this process, the feces are prepared in a fluid that causes the parasites to float to the top, allowing them to be visually inspected under a microscope for identification. If an organism is identified through fecal flotation, it is likely present in significant amounts in the animal. However, there are situations where infections can be missed, typically occurring early in the infection, with chronic infections that intermittently shed, or when diarrhea is so severe that collecting a good sample is difficult. The alternative method is PCR (polymerase chain reaction), which tests for the presence of DNA from certain infectious organisms. These tests are very sensitive and can detect even minute amounts of DNA in the sample, resulting in fewer false negatives. However, they can also detect the presence of parasites that are not currently causing a problem for the animal. PCR is still limited by intermittent shedding, as the material must be present to be detected.

Intermittent shedding is one of the reasons a dog is not considered to be negative until 3 samples taken days apart are all negative. In a healthy dog with normal stool, the 3 sample technique is rarely done, but in an ill dog this is why repeated testing is done even when the originals were normal.

External Parasite Testing

Heartworm and Tick borne disease testing are usually ELIZA tests looking for antigen (specific portion of the organism) or antibodies (flags the dog's body makes to identify antigen as not self to the body). If present the test will bind resulting in a positive test. These tests help determine if your dog has been exposed, but do not necessarily mean they are actively infected. If your dog gets a positive on these tests, there will likely be follow up testing to determine if treatment is needed.