Magnetic antibody immunoassay thyroid function tests in general practice

Commercial radioimmunoassay kits for the measurement of human total thyroxine (T4) and total triiodothyronine (T3) based on magnetic separation are discussed for use in dogs and cats. The T4 assay procedure is modified to increase the accuracy over normal canine and feline ranges using four standards from kit components provided. Results of validation are presented and indicative normal ranges given: canine T4, 0.94 to 3.45 micrograms/dl; canine T3, 0.36 to 1.52 ng/ml; feline T4, 1.34 to 4.70 micrograms/dl; feline T3, 0.23 to 0.95 ng/ml. There is a significant breed difference in T4 levels between poodles and Yorkshire terriers.