Introduction
Blood tests are an important diagnostic tool that allow veterinarians to evaluate a dog’s overall health and detect any underlying conditions or diseases. Conducting routine blood work provides vital information about how a dog’s organs are functioning and can help establish baseline values for comparison later on. There are many different types of canine blood tests available, which can broadly be categorized into complete blood counts, chemistry panels, tests for specific diseases, and more advanced tests like cultures or coagulation profiles. Understanding common blood tests for dogs, why they may be recommended, and how to interpret the results can help owners partner with their veterinarian to provide the best care.
Complete Blood Count (CBC)
A complete blood count (CBC) is a common blood test performed on dogs that measures different components and features of your dog’s blood. It provides important information about red blood cells, white blood cells, platelets, and other factors.
Components measured in a CBC include:
- Red blood cell (RBC) count – The number of red blood cells per volume of blood. Low RBC can indicate anemia.
- Hemoglobin (Hgb) – A protein in RBCs that carries oxygen. Low Hgb can also indicate anemia.
- Hematocrit (HCT) – The percentage of blood volume made up of RBCs. Low HCT is another sign of anemia.
- Mean corpuscular volume (MCV) – The average size of RBCs.
- White blood cell (WBC) count – The number of white blood cells per volume of blood. Elevated WBCs often indicates inflammation or infection.
- Platelet count – Platelets help the blood clot. Low platelets is called thrombocytopenia.
Reference ranges for CBC results in dogs: Hematology (Complete Blood Count) Reference Ranges
RBC: 5-10 x 10^6/uL
Hgb: 12-18 g/dL
HCT: 37-55%
MCV: 60-77 fL
WBC: 6-17 x 10^3/uL
Platelets: 200-500 x 10^3/uL
Chemistry Panel
A chemistry panel is a common blood test that provides important information about a dog’s overall health and organ function. The test measures levels of enzymes, electrolytes, and other substances in the blood to screen for conditions affecting the kidneys, liver, pancreas, and other organs.
Some of the most important components of a dog chemistry panel include:
- ALP (alkaline phosphatase) – indicates liver or bone disease
- ALT (alanine aminotransferase) – indicates liver disease
- BUN (blood urea nitrogen) – indicates kidney function
- Creatinine – indicates kidney function
- Glucose – indicates diabetes or other metabolic conditions
- Total protein – indicates dehydration or liver disease
- Albumin – indicates liver or kidney disease
- Calcium – indicates parathyroid, kidney, or bone disease
- Phosphorus – indicates kidney disease
- Sodium, potassium, chloride – indicate electrolyte imbalances
It’s important to compare a dog’s test results to normal reference ranges to determine if any values are abnormally high or low. Normal ranges can vary slightly between veterinary laboratories but generally fall within the following ranges (Reading the Blood Chemistry Panel: An Art and Science – PetMD):
- ALP: 15-150 U/L
- ALT: 12-130 U/L
- BUN: 6-31 mg/dL
- Creatinine: 0.5-1.8 mg/dL
- Glucose: 70-125 mg/dL
- Total Protein: 5.0-7.8 g/dL
- Albumin: 2.7-4.5 g/dL
- Calcium: 8.9-11.4 mg/dL
- Phosphorus: 2.5-6.1 mg/dL
- Sodium: 141-152 mEq/L
- Potassium: 3.6-5.5 mEq/L
- Chloride: 102-117 mEq/L
Abnormal chemistry panel results will prompt a veterinarian to run additional tests to diagnose the underlying cause. Trends in test results over time also provide important insight into a dog’s health.
Thyroid Tests
Thyroid tests check the levels of thyroid hormones like thyroxine (T4) and triiodothyronine (T3) to evaluate thyroid function in dogs. The main tests include:
- Total T4 (TT4) – measures total circulating T4 hormone levels. Normal range is around 1-4 μg/dl, but can vary by lab. Low T4 may indicate hypothyroidism.
- Free T4 (fT4) – measures unbound T4 available to body tissues. Normal is around 0.7-3.6 ng/dl. Low levels can indicate hypothyroidism.
- Total T3 (TT3) – measures total circulating T3 levels. Normal is around 45-150 ng/dl. Low T3 can be seen with non-thyroidal illness.
- Free T3 (fT3) – measures unbound T3 available to tissues. Normal range is around 1.5-5 ng/dl.
Interpreting thyroid levels requires assessing the clinical picture. Normal ranges can vary by laboratory. Low T4 with normal T3 may indicate early hypothyroidism. Checking multiple thyroid values can help confirm any abnormalities. Thyroid testing may need to be repeated over time to definitively diagnose thyroid disease.
Heartworm Test
Heartworm disease is caused by parasitic worms called Dirofilaria immitis that live in a dog’s heart and pulmonary arteries. Mosquitoes transmit the larvae, which mature into worms over several months. The worms can cause lung disease, heart failure, organ damage, and even death in severe cases.
To diagnose heartworm infection, veterinarians use a blood test that detects antigens produced by adult female worms. This antigen test is very accurate, with a specificity approaching 100% according to research. However, no test is perfect, and false positives are possible in certain situations like after heat treatment for cancer. Confirmation may require checking for microfilariae and imaging tests.
Sources:
Heartworm Diagnostics: Antigen Tests Alone Aren’t Enough
Effects of diagnostic test accuracy and treatment efficacy on …
Lyme Disease Test
Lyme disease is a bacterial infection caused by Borrelia burgdorferi that is transmitted by ticks. It is one of the most common tick-borne diseases that affects dogs. Lyme disease in dogs initially causes fever, loss of appetite, and lethargy. As it progresses, it can lead to kidney disease, heart disease, and neurological disorders.
Veterinarians use several tests to check for exposure to Lyme disease in dogs. These include the SNAP 4DX Plus, Accuplex 4, and VetScan Lyme rapid tests. These tests look for antibodies produced by the dog’s immune system in response to proteins found on B. burgdorferi bacteria. If antibodies are detected, it indicates the dog has been exposed to Lyme disease at some point.
A positive Lyme test does not necessarily mean the dog is currently infected or will develop clinical symptoms. It only shows exposure. Dogs in early stages of infection can test negative. Veterinarians may recommend follow-up testing and additional diagnostic tests if Lyme disease is suspected based on symptoms.
According to Cornell University, the C6 antibody test specifically detects antibodies to the C6 protein of B. burgdorferi [1]. This protein is produced throughout the course of Lyme infection, so the C6 test can identify later stages of the disease. It has high sensitivity and specificity for confirming Lyme disease diagnosis.
Interpreting Lyme test results requires assessing antibody levels along with the dog’s clinical signs and risk of tick exposure. Positive results indicate exposure at some point, but dogs may test positive for months to years after initial infection. Negative results cannot fully rule out early or active infection in dogs showing symptoms potentially related to Lyme disease.
Urinalysis
A urinalysis evaluates kidney function and can detect signs of disease or inflammation in a dog’s urinary tract. It checks multiple parameters in a urine sample including color, clarity, specific gravity, pH, protein, glucose, ketones, bilirubin, blood, white blood cells, crystals, casts, and bacteria.
Specific gravity measures the concentration of particles in the urine. Normal dog specific gravity ranges from 1.015 to 1.045. A reading outside of this range could indicate kidney problems. Dogs normally have acidic urine with a pH between 5.5 and 7.0. Alkaline urine over 7.5 may indicate a UTI or bladder stones. The presence of protein, glucose, blood, or white blood cells in high levels points to medical issues needing further evaluation.
Microscopic examination of the sediment can identify crystals, casts, red and white blood cells, and bacteria. Struvite, calcium oxalate, or urate crystals suggest bladder stones. Casts are cylinders of protein indicative of kidney dysfunction. Too many red blood cells indicates bleeding in the urinary tract. White blood cells point to inflammation or infection. Finding bacteria guides antibiotic selection if a UTI is suspected.
Understanding what is normal and abnormal in dog urinalysis results helps veterinarians diagnose the underlying cause and determine appropriate treatment (Urinalysis – VCA Animal Hospitals, 2023). Careful interpretation of all urinalysis parameters together provides key insights into a dog’s health.
Blood Culture
Blood cultures are often taken in dogs when there is a suspected bloodstream infection or sepsis (https://www.vet.cornell.edu/animal-health-diagnostic-center/testing/protocols/blood-culture-technique). They involve collecting a blood sample and incubating it in special media to allow any bacteria or fungi present to multiply to detectable levels that can later be identified (https://pubmed.ncbi.nlm.nih.gov/34606667/).
Positive blood culture results indicate the presence of bacteria or fungi circulating in the dog’s bloodstream. This confirms that the dog has a bloodstream infection rather than just a localized infection contained in one area of the body. The organisms grown from the culture allow the veterinarian to identify the specific cause of infection and select the appropriate antibiotic treatment (https://pubmed.ncbi.nlm.nih.gov/6365865/).
Some common infections that may lead to positive blood cultures in dogs include sepsis, pyometra, discospondylitis, bacterial endocarditis, and infected catheters or intravenous lines. A positive blood culture provides key evidence to guide treatment when systemic signs of infection are present but the source is unknown.
Coagulation Tests
Coagulation tests measure how long it takes for blood to clot. The two main coagulation tests performed on dogs are:
- Prothrombin Time (PT) – measures the clotting ability of the extrinsic coagulation pathway.
- Activated Partial Thromboplastin Time (APTT) – measures the intrinsic coagulation pathway.
Prolonged clotting times in these tests may indicate coagulation factor deficiencies, vitamin K deficiency, liver disease, or treatment with anti-coagulant drugs like heparin or warfarin. Shortened clotting times can sometimes occur with hypercoagulable states.
Normal reference ranges for coagulation tests in dogs:
Conclusion
Understanding your dog’s blood test results is critical for monitoring their health and catching any abnormalities early. Blood tests allow veterinarians to check for signs of infection, anemia, clotting issues, organ problems and more. If any results come back abnormal, it’s important to follow up with your vet right away to determine next steps. They may recommend further testing like imaging or biopsies to get a definitive diagnosis. From there, you can work with your vet to come up with a treatment plan which may include medications, dietary changes, or procedures. While abnormal results can be scary, the earlier a problem is identified, the better the chances of successful management. With proper care guided by blood test findings, your dog can continue to lead a happy and healthy life.
