Laboratory testing methods for pets
An overview of the different laboratory testing methods used in veterinary medicine to help diagnose illness and injury in animals.
Laboratory testing methods on animals
When it comes to diagnosing disease and illness in animals, they cannot voice the symptoms they are feeling and so a vet depends only on the clinical signs that can be seen and any results that laboratory testing provides. There are many different kinds of testing methods, and all of them are used in human medicine as well.
Blood tests are very common as they can show so much. Not only can the results tell a vet what is wrong with your pet, but also how sick they are. The result of a blood test can often help the vet decide on the next step they will take in order to treat an animal, and they can also show how well an animal is responding to treatment already given.
Blood is usually taken from a vein in the front leg, which often requires hair to be clipped away hence that bald patch that pets normally come home with after they have had a short stay at the vets. However, sometimes blood will be taken from a vein in the back leg or jugular (neck), depending on how easy it is to find a vein. Sometimes when an animal is particularly ill, or if they have low blood pressure, it is easier to find an accessible vein in the neck than it is in the leg.
Once the blood has been taken, it is stored in a tube. There are many different kinds of tube, and the one chosen will depend on what type of blood test needs. There are three main kinds of sample preparation used within veterinary medicine:
•Whole blood – this blood needs to be kept fresh and so is contained in a tube holding anti-coagulant, usually heparin, to stop the blood from clotting.
•Plasma – this is the cellular part of the blood. It is taken by using whole blood, and separating the ‘heparinized plasma’ using a centrifugal machine. The machine spins very fast so that the blood separates. The clean plasma can then be removed from the top of the blood.
•Serum – once blood has clotted, the remaining free-flowing fluid is known as serum. The clot is removed and the remaining serum is used.
Smears and stains are created using a tiny drop of whole blood drawn up using a capillary tube. The smears are then placed on glass slide and drawn across using a second slide. The smears can then be examined under a microscope. Stains are created by placing a small drop of blood on the slide with a stain, Diff-Quik for instance, which in turn stains certain parts of the blood cells, helping the vet to identify the different cells, and any mutated cells.
For most diagnosis purposes, a full blood count (FBC) is used. This is where whole blood and plasma are used to create a biochemistry analysis. By comparing the results to the general average, a vet can determine whether an infection is present, or if certain conditions like diabetes are a risk. Using these results alongside other signs such as temperature, respiratory rate and pulse, a vet can diagnose an animal correctly.
Urine and Feces Tests
Urine tests are commonly used to help diagnose conditions such as urinary infections and diabetes. Using a dipstick test and measuring the amount of blood, glucose and protein within the urine can help a vet to determine the next step of treatment. Another test performed on urine is to place it on a slide and look at it under a microscope. This can show up crystals within the urine, common in urinary infections. Not only this, but a vet can tell what type of crystal is there, which will help to decide on the type of treatment to give.
Fece tests are normally used to find parasites, but can also help to find pathogens such as Salmonella. This is normally done by mixing the feces with some water and then placing the mixture on a slide underneath a microscope.
Bodily Fluid Tests
Sometimes bodily fluids can be extracted from the abdomen, chest, joints or spine. Fluid build up can be the result of an infection or underlying condition. The fluid can be tested the same way blood is. More often than not, bodily fluids are sent away to an external laboratory for extensive testing. A vet will then use the results to decide whether drugs or surgery are needed.
Skin scrapings using a surgical blade and slide, are placed under a microscope. These can be used to check for external parasites such as mites and lice as well as fungal skin infections. Occasionally hair will also be taken to test the roots of the hair.
If lumps and tumors are present, a vet will take a small part of the lump and send it away for testing. This is called a biopsy. Biopsies are used mainly to determine whether a tumor is malignant (cancerous) or benign (non-cancerous).
Laboratory testing is important in any medical profession, but in veterinary medicine where the patient cannot voice their emotions and feelings, it can help determine the condition, disease or illness so that treatment can begin. Sadly, laboratory testing can be expensive, but with good pet insurance this need not be a problem. Help to avoid needing these tests by keeping your pet fit and healthy with regular vaccinations and parasite treatment.
Sources: B.S.A.V.A Veterinary Nursing Second Edition edited by D.R Lane & B. Cooper
B.S.A.V.A Manual of Veterinary Nursing edited by Margaret Moore