Blood biochemistry: overview

Overview

• 
  Measuring serum or plasma levels of nutrients, metabolites, enzymes, etc can provide general or specific data about organ function and disease processes.Print-off the owner factsheet on ' Samples - how they help your vet ' to give to your client.
• Parameters measured include:
  • Total protein .
  • Albumin .
  • Total globulin .
  • Gamma globulins .
  • Sodium .
  • Potassium
  • Chloride .
  • Bicarbonate .
  • Calcium .
  • Phosphate .
  • Copper .
  • Cobalt.
  • Selenium.
  • Lead.
  • Iron .
  • Urea .
  • Creatinine .
  • Ammonia .
  • Glucose .
  • Fructosamine .
  • Bile acids .
  • Bilirubin - direct and total .
  • Cholesterol .
  • Triglycerides .
  • Glycerol.
  • Free fatty acids.
  • Creatinine kinase .
  • Aspartate aminotransferase (ALT) .
  • Alanine aminotransferase (AST) .
  • Gamma glutamyltransferase (GGT) .
  • Alkaline phosphatase (ALP) .
  • Amylase .
  • Lipase .
  • Trypsin-like immunoreactivity (TLI) .
  • Hormones: cortisol , thyroxine ; parathyroid hormone .
  • Vitamin B12 .
  • Folate .
  • Para-aminobenzoic acid .
  • C reactive protein.

Uses

In combination

• Biochemical tests are useful only when combined with clinical data from history and physical examination of the patient.

Result data

Normal (reference) values

• Reference intervals are usually established based on statistical determination of values which includes 95% of the population of normal animals.
• This means that 5% of normal animals have a value outside this range.
• The more tests that are performed the greater the chance of one of these being outside the normal range in a healthy animal.
  Do not base a clinical diagnosis on one test result..
• Reference intervals are dependent on test method used.
• Individual laboratories should supply reference intervals for their tests.
• Information about numbers and types of animals used for determination of reference intervals and statistical methods used should be available by request.

Errors and Artifacts

• Poor handling of sample prior to testing particularly:
  • Lipemia (inadequate fasting).
  • Hemolysis (traumatic sampling or prolonged storage).
• Test inaccurately performed (unlikely in commercial laboratory, more common in practice laboratory).
• Sample collected into inappropriate transport medium or anticoagulant (see sample tube prefence table ).
• Over interpretation of results.

• Artefactual hemolysis may be caused by:
  • Sampling with wet needle or syringe.
  • Traumatic sample technique, ie excessive suction applied to syringe with small needle.
  • Trauma with shaking sample to mix anticoagulant.
  • Prolonged storage before separation.
  • Centrifugation in an unbalanced centrifuge.

Sources

Publications

Other sources of information

• Kaneko J J, Harvey J W & Brass M L (eds) (1997) Clinical Biochemistry of Domestic Animals. 5th edn. Boston: Academic Press.