Labwork in Review (or: What do all these values mean?!)

We draw blood and collect urine so we can run these tests and determine the health status of our feline patients, but what do all those initials and values mean? Our lovely head technician Vanessa has compiled this overview to help us understand what all those letters and numbers mean.

Liver Values: (ALT, AST, ALKP, TBILI, GGT,CHOL, proteins)

  1. 1. ALT- Alanine aminotransferase is an enzyme found in liver cells. Damaged liver cells leak this enzyme which translates to increased quantities in the blood. This is a specific indicator of liver disease. It can be elevated without the cat being ill, if the thyroid level is high.
  2. AST- Aspirate aminotransferase is an enzyme found in many cells in the body, including the liver, heart and muscles.
  3. ALKP- Alkaline phosphatase is an enzyme present in the liver, bone, intestine or kidneys. Increases related to the liver can be caused by a blocked bile duct, actions of some drugs (such as steriods or phenobrabitol) or Cushing’s disease (hyperadrenocorticism). It can also be elevated in growing youngsters.
  4. TBILI (Total Bilirubin)- Bilirubin is a bile pigment that may be elevated in the blood if bile flow is obstructed or if the patient has Immune Mediated Hemolytic Anemia (IMHA) or any kind of anemia that involves red blood cell destruction (such as mycoplasma infection). It can be elevated without any other values being elevated if the cat has pancreatitis. It is often elevated in cats with liver disease and is the reason that icteric cats are yellow.
  5. ALBUMIN- Albumin is a plasma protein that is one half of the total protein level we check as part of the PCV/TP. A low albumin level can cause death if left untreated.
  6. GLOBULIN- is a plasma protein that is the other half of the TP reading. Elevations in globulins can be due to immune response, oral disease and illnesses like Feline Infectious Peritonitis (FIP).

Kidney Values: (BUN, CREA, PHOS, AMYL, ALB, URINARY SG, MICROALBUMIN, ELECTROLYTES)

  1. BUN (Blood Urea Nitrogen)- is made by the liver as a breakdown of dietary proteins related to ammonia. Increased BUN levels are indicative of kidney disease, decreased circulation to the kidneys and/or urinary  obstruction. If the BUN is elevated and the CREA is normal, it is possible that there is a GI bleed or, less likely, intestinal parasites.
  2. CREA (Creatinine)- is a by-product of phosphocreatine, a molecule involved in energy production in the skeletal muscles. It is basically a measure of permanent kidney damage. Keep in mind that elevation in the BUN/CREA levels isn’t seen until 75% or greater of the kidney function has been lost.
  3. Phosphorus- This is a by-product of food breakdown that is excreted by the kidneys. It is generally increased in cats with chronic renal dysfunction.
  4. Potassium- is a mineral that is essential for proper functioning of the heart, muscle, kidneys, nerves and digestive systems. Excessive elevations (hyperkalemia) in potassium can cause fatal cardiac arrythmias, as can hypokalemia. Cats with renal failure commonly present with hypokalemia due to urinary excretion of potassium. Additionally, cats with urinary blockages can have greatly increased levels of postassium.
  5. PCV (Packed red Cell Volume)- is a value that tells us whether or not the animal is anemic. Kitties that have chronic renal disease are always at risk of anemia because the kidneys excrete erythropoietin, the hormone that tells the bone marrow to produce red blood cells.
  6. Urinary Specific Gravity- This is a measure of how well the kidneys concentrate the urine. If the SG is below 1.035, it is an indicator that renal function is in some way compromised. HOWEVER, cats that eat a diet primarily of canned food or if they eat food with added water, the SG can be lower.
  7. Microalbumin- is a protein that is excreted in the urine. Experts are not sure if the protein causes worsening of the disease process or if the disease process causes the protein to be excreted. Whatever the reason, an elevated urine microalbumin means that the patient is far more likely to have a poor outcome to a medical challenge that an animal that doesn’t have it.

PANCREAS (SPEC FPL, GLUCOSE, AMYLASE, LIPASE)

  1. SPECIFIC FPL (feline pancreas-specific lipase)- This is a snap test that will  help diagnose or rule out pancreatitis in cats without a specific number attached. A positive specific fPL is indicative of pancreatitis.
  2. GLUCOSE- this checks the level of sugar in the blood. Glucose values can be elevated in cats due to diabetes or stress. Stress elevations in the BG should not cause the value to measure much over 250 mg/dL. If the blood levels exceed this, it is possibly due to diabetes mellitus.
  3. AMYLASE & LIPASE- both of these enzymes are excreted by the pancreas for food digestion. Elevations in these levels are clinically insignificant in cats. In dogs, elevations in amylase and lipase are indicative of pancreatitis.
  4. FRUCTOSAMINE– Checking this level can help differentiate between diabetes and stress elevations in the BG levels. If the value is high, it means that the BG has been elevated for a period of time and the cat is likely diabetic, rather than just stressed. When monitoring fructosamine in diabetic cats, if the levels are less than 500, it means that the diabetes is well-controlled.

THYROID

  1. THYROID- Thyroxin is a hormone produced by the thyroid gland, and overproduction of this thyroid hormone causes hyperthyroidism in cats. Hyperthyroidism is caused by a (usually) benign tumor of the thyroid gland. The total T4 test measures the amount of thyroxin being released in the body at the time of the blood draw. The free T4 test is a measure of the thyroxin present over a period of time, so it measures how much thyroxin is circulating in the body. Hyperthyroidism causes the body to run at a higher basal metabolic rate and can cause high blood pressure, detached retinas, gastrointestinal issues, hair loss, hyperactivity, congestive heart failure, kidney failure and eventually death.

URINALYSIS (STRIP, SG, SEDIMENTATION)

  1. STRIP- The urine strip measures the pH (normal is 6.3- 6.5), blood, bilirubin, protein (cats ALWAYS have protein on the strip), glucose, ketones, urobilinogen, and nitrites.
  2. SPECIFIC GRAVITY- Urinary Specific Gravity- This is a measure of how well the kidneys concentrate the urine. If the SG is below 1.035, it is an indicator that renal function is in some way compromised. HOWEVER, cats that eat a diet primarily of canned food or if they eat food with added water, the SG can be lower.
  3. SEDIMENTATION- This is performed to confirm the presence of blood, white blood cells (WBC’s), bacteria, cells, casts, crystals, and/or urinary parasites (such as capillaria).

CBC: Differential

LEUKOCYTES (NEUTROPHILS, LYMPHOCYTES, MONOCYTES, EOSINOPHILS, BASOPHILS)

  1. Neutrophils- These cells are sent out in response to infection or inflammation. They are about twice the size of red blood cells. The nucleus stains dark purple and the cytoplasm stains pale pink. In normal animals a healthy neutrophil nucleus will have two to four lobes. Neutrophils should comprise about 60-65% of the WBC’s seen on a differential.
    Immature neutrophils are also known as bands and are a direct sign of infection. The nucleus on bands is usually horseshoe shaped, the ends larger and rounded, with no ‘pinching’ or segmentation.
    Hypermature neutrophils are also known as toxic neutrophils.

    Neutrophil

    Band

Toxic Neutrophil

2.   Lymphocytes- These cells are usually seen as an acute response to a viral infection and are responsible for forming antibodies and antigenic response. The cell nucleus  stains purple with a thin band  of pale blue cytoplasm. In normal animals, the majority are mature, smaller cells that are 1.5 to 2 times the size of red blood cells. These should be approximately 30-40% of the cells seen.

Lymphocyte

3. Monocytes- these cells are normally a chronic response to infection, stress response, infectious processes or inflammation. On a CBC/Diff, about 8% monos may be seen on a normal animal.

Monocyte

4. EOSINOPHILS-  These cells are released in response to allergies, GI inflammation, or (usually) parasitism. Eosinophils are about the same size as neutrophils, or about twice the size of RBC’s.  The nucleus is lobulated or partially segmented and stains dark purple.  The cytoplasm stains a light blue color and contains red granules.  Feline eosinophils have small, rod-shaped granules. Maybe 2% of the leucocytes seen on a differential will be eosiniphils on a normal healthy cat.

Eosinophil

5. BASOPHILS- These cells are rarely seen in cats, but they are produced in response to severe allergies or severe parasitism.  Basophils are about the same size as neutrophils.  The nucleus is lobulated or partially segmented and often appears coiled.  The cytoplasm stains a blue to grey color and contains granules that vary in color from lavender to black.  The color and quantity of the granules vary with the species.   Feline eosinophils have numerous lavender granules.

basophil

An easy way to remember the correct proportions of the leucocytes in a differential (courtesy again of Vanessa) is to think of the phrase, “Never Let My Engine Blow, 60, 40, 8, 2, 0.” Yeah, I know, it doesn’t add up to 100%, but it gets the idea across.

THROMBOCYTES:

  1. PLATELETS- play a crucial role in the clotting of blood, along with all the clotting factors that are produced by the liver.

Platelets with a normal eosinophil
Courtesy of the Nottingham Vet School

ERYTHROCYTES

  1. RED BLOOD CELLS (RBC’s)- These are the cells that carry oxygen from the lungs to our tissues. Anemia (a deficiency in RBC’s) can be cause by blood loss, decreased production of new cells and/or RBC destruction. Anemia can be severe enough to result in death.

Top to bottom: 2 neutrophils with platelets below, lymphocyte, eosinophil, monocyte. All cells reported as unremarkable.

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About debikm

I am a veterinary technician by day, a wannabe writer the rest of the time. Living in a fantasy world is one of my greatest pleasures. Too bad it doesn't pay the bills...
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2 Responses to Labwork in Review (or: What do all these values mean?!)

  1. Hilz says:

    Wow! I am impressed!!! VERY nice!!

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