Diagnostic value of alkaline phosphatase isoenzyme separation by affinity electrophoresis in the dog

Affinity electrophoresis, using wheat germ lectin, was used to separate the alkaline phosphatase isoenzymes in the sera of 150 dogs with alkaline phosphatase values greater than or equal to 150 IU/L. The method provided clearer separation of the liver, bone and steroid-induced alkaline phosphatase isoenzymes commonly observed in canine serum, compared to conventional cellulose acetate electrophoresis. The dogs were divided into four patient groups determined by previous corticosteroid treatment, evidence of elevated endogenous corticosteroid levels, age and alanine aminotransferase values. The isoenzyme pattern of each patient was qualitatively assessed. The isoenzyme pattern most frequently observed was greater than 50% steroid induced alkaline phosphatase, which was present in 76 of 150 dogs. This pattern was observed in 18 of 22 dogs receiving corticosteroid therapy, two of three dogs with hyperadrenocorticism, and in dogs with a variety of other diagnoses. The majority of immature dogs (12 of 20) had an isoenzyme pattern consisting of greater than 50% bone. The majority of dogs with active hepatocellular injury (16 of 27) had greater than 50% liver isoenzyme. The isoenzyme pattern was not specific for certain diseases, therefore the diagnostic usefulness is limited. However the isoenzyme result is useful in some cases to determine which further diagnostic tests are indicated, and to determine the source of alkaline phosphatase elevation.