D80
Blood (Serum) Chemistry

Description: The serum chemistry profile is one of the most important initial tests commonly performed on animals. A blood sample is collected from the horse. The blood is then separated into a cell layer and serum layer by spinning the sample at high speeds in a machine called a centrifuge. The serum layer is drawn off, and a variety of compounds are then measured. These measurements aid the veterinarian in assessing the function of various organs and body systems.

Diagnostic Value: Very high. Sometimes a specific diagnosis may be made on the basis of a blood chemistry profile alone. More often than not, however, the profile provides information on a variety of body organs and systems that gives the doctor an indication of where a problem might be located. The profile can be extremely helpful in determining which of the many other diagnostic tests would be beneficial.

Risks to Patient: Virtually none, providing that the blood is collected under sterile conditions by a trained professional.

Relative Cost: Low.

Normal Ranges: The following is a list of the normal ranges in horses for some of the major parameters on a chemistry profile. These numbers can vary from laboratory to laboratory.

Glucose: 75-110 mg/dl
Blood Urea Nitrogen (BUN): 12-27 mg/dl
Creatinine: 1.2-2.0 mg/dl
Calcium: 12.0-13.7 mg/dl
Phosphorus: 2.9-4.1 mg/dl
Total protein: 5.8-7.9 g/dl
Albumin: 2.3-3.7 g/dl
Alkaline Phosphatase (ALP): 86-290 IU/L
Aspartate Aminotransferase (AST): 140-400 IU/L
Sorbitol Dehydrogenase (SDH): 0-9 IU/L
Creatine Phosphokinase (CPK): 120-450 IU/L
Chloride: 99-111 mEq/L
Potassium: 2.4-4.6 mEq/L
Sodium: 132-145 mEq/L

Interpretation of Results:

  1. Glucose - This is a measurement of the blood sugar level.
    1. High glucose levels can occur during stressful situations and in association with the use of certain drugs (steroid administration).
    2. Low glucose levels can occur when an animal does not eat or when there is a severe bacterial infection in the bloodstream.

    2.
  2. Blood urea nitrogen (BUN) - Urea, which is normally excreted by the kidney, is a by-product of protein metabolism.
    1. High levels of BUN may be the result of kidney disease or blockage of the normal flow of urine (from a kidney or bladder stone, for example).
    2. Low BUN levels can result from a low protein diet or liver disease.

  3. Creatinine - This is a by-product of muscle contraction that is normally excreted by the kidney.
    1. High creatinine levels are found with kidney disease or other problems that prevent the kidney from normally excreting creatinine.

  4. Calcium - Calcium, a mineral normally found in the body, is important for normal muscle and heart function.
    1. High calcium levels may be the result of some plant intoxications, some types of cancer, excessive dietary supplements, kidney disease, and a variety of other conditions.
    2. Low calcium levels can occur in lactation tetany, transport tetany, and diaphragmatic flutter.

  5. Total Protein - Several protein types circulate in the bloodstream. These protein types can be measured all together or may be separated out and measured one at a time. On a routine blood chemistry profile, total protein is measured as the total of all proteins together. Albumin, the most abundant protein type, is usually measured separately.
    1. High protein levels may result from colitis, Potomac horse fever, choke, botulism, certain clostridial and bacterial infections, salt toxicity, lead toxicity, certain toxic plants, abscesses, and equine infectious anemia.
    2. Low protein levels can occur in situations of malnutrition, parasitism, intestine absorption problems, blood loss, certain infectious diseases, and kidney or liver disease.

  6. Alkaline Phosphatase (ALP) - This is an enzyme found in liver and bone cells.
    1. High ALP levels may indicate a liver problem or pyrrolizidine alkaloid toxicity. High levels of ALP can be normal in growing foals.

  7. Aspartate Aminotransferase (AST) - This is another enzyme produced by a variety of tissues. Concentrations tend to be highest in muscle and liver cells.
    1. High AST levels occur most often when the muscles and/or the liver are damaged. This damage can occur because of toxins, lack of oxygen, inflammation, metabolic disorders, and other diseases.

  8. Sorbitol Dehydrogenase (SDH) - This is another liver specific enzyme.
    1. High levels of SDH can indicate liver damage and intestinal problems.

  9. Creatine Phosphokinase (CPK) - This is an enzyme found in muscle cells.
    1. High CPK levels can occur in situations where muscles of the body are damaged, diseased, or inflamed (equine influenza and exertional rhabdomyolysis). This can even occur with heart muscle problems. Selenium and vitamin E deficiencies are also a cause for elevated CPK levels in the horse.

  10. Chloride - This is a negatively-charged electrolyte (dissolved salt).
    1. High levels of chloride can occur with diarrhea, dehydration, fluid therapy, and acidosis (where the pH of the body is abnormally low).
    2. Low levels of chloride can occur with excessive sweating, blood loss, kidney disease, and alkalosis (where the pH of the body is abnormally high).

  11. Potassium - This is an electrolyte with a positive charge.
    1. High levels are associated with acidosis (where the pH of the body is abnormally low), kidney disease, and some treatments or syndromes.
    2. Low levels are seen with diarrhea, certain phases of kidney disease, and the administration of some drugs.

  12. Sodium - This is also another electrolyte with a positive charge.
    1. High sodium levels may accompany dehydration (due to diarrhea, diuretics, etc.) and salt poisoning.
    2. Low sodium occurs with diarrhea, blood loss, excessive sweating, fluid therapy, and kidney problems.

Note: This section lists only a few of the most common possibilities for changes in a chemistry profile. A physical examination, additional history, and other tests may be required before a specific diagnosis can be determined.