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Clinical biochemistry refers to the analysis of the blood plasma (or serum) for a wide variety of substances

—substrates, enzymes, hormones, etc—and their use in the diagnosis and monitoring of disease.

Analysis of other body fluids (eg, urine, ascitic fluids, CSF) is also included. One test is very seldom

specific to one clinical condition, and basic checklists of factors affecting the most commonly-requested

analytes are given below. Thus, rather than 6 tests that merely confirm or deny 6 possibilities, a well-

chosen group of 6 tests can provide information pointing to a wide variety of different conditions by a

process of pattern recognition. Biochemistry tests should be accompanied by full hematology, as

evaluation of both together is essential for optimal recognition of many of the most characteristic disease

patterns (see Diagnostic Procedures for the Private Practice Laboratory: Clinical Hematology).

Basic Test Panel

Most veterinary laboratories offer a basic panel of tests, which represents a minimal investigation

applicable to most general situations. For small animals, a typical panel includes total protein, albumin,

globulin (calculated as the difference between the first 2 analytes), urea, creatinine, ALT, and alkaline

phosphatase (ALP). In addition, a yellow color seen in the plasma should be considered an indication for

measuring bilirubin. This panel may be modified as appropriate for other species, eg, glutamate

dehydrogenase (GDH) and/or γ glutamyltransferase (γ GT) are more appropriate “liver enzymes” for

horses and farm animals, or it may be more appropriate to concentrate primarily on muscle enzymes (CK

and AST) in athletic animals.

Total protein increases due to dehydration, chronic inflammation, and paraproteinemia. It decreases due

to overhydration, severe congestive heart failure (with edema), protein-losing nephropathy, protein-losing

enteropathy, hemorrhage, burns, dietary protein deficiency, malabsorption, and some viral conditions

(especially in horses).

Albumin increases due to dehydration. It decreases due to the same factors as total protein, plus liver

failure.

Urea increases due to excess dietary protein, poor quality dietary protein, carbohydrate deficiency,

catabolic states, dehydration, congestive heart failure, renal failure, blocked urethra, and ruptured

bladder. It decreases due to low dietary protein, gross sepsis, anabolic hormonal effects, liver failure,

portosystemic shunts (congenital or acquired), and inborn errors of urea cycle metabolism.

Creatinine increases due to renal dysfunction, blocked urethra, and ruptured bladder. It decreases due to

sample deterioration. Patients with a high muscle mass have high-normal creatinine concentrations, while

patients with a low muscle mass have low-normal creatinine concentrations.

ALT increases due to hepatocellular damage, muscle damage, and hyperthyroidism.

ALP increases due to increased bone deposition, liver damage, hyperthyroidism, biliary tract disease,

intestinal damage, Cushing's disease, corticosteroid administration, barbiturate administration, and

generalized tissue damage (including neoplasia).

GDH increases in hepatocellular damage, particularly hepatic necrosis in horses and ruminants.

γGT increases in longer-term liver damage; it is particularly useful in horses and ruminants.

CK, the classic “muscle enzyme,” increases markedly in rhabdomyolysis and aortic thromboembolism.