Measurement of total thyroxine concentration in serum from dogs and cats by use of various methods

Abstract

Objective-To compare results obtained from assay of total thyroxine (T 4 ) concentration in serum of dogs and cats by use of 4 methods. Sample Population-Serum samples obtained from 98 dogs and 100 cats and submitted by veterinarians to an endocrine testing laboratory. Procedure-Total T 4 concentration was determined in each sample by use of 4 assay methods. Assay methods included a radioimmunoassay (RIA) marketed for use in dogs, an RIA for use in humans, a chemiluminescent enzyme immunoassay for use in humans, and an in-house ELISA. Results-Total T 4 concentrations obtained by use of all methods were significantly correlated. Bias-plot comparison revealed similar good overall agreement. Total T 4 concentrations determined by use of the RIA marketed for use in dogs were generally lower than concentrations measured by use of the other methods. Clinical comparisons were made by evaluation of the T 4 results in the context of the reference range recommended by each laboratory. A difference was found for clinical comparisons on the basis of T 4 assay method when used to identify dogs as possible hypothyroid suspects. This difference was related more to the reference range used than to the absolute T 4 value. The number of hyperthyroid-suspect cats with T 4 values greater than the reference range was the same for each of the 4 assay methods. Conclusions and Clinical Relevance-Total T 4 concentrations determined in dogs and cats by use of 4 commonly used methods provided similar and consistent results. (Am J Vet Res 2006;67:259-265) T 4 Thyroxine RIA Radioimmunoassay CEIA Chemiluminescent enzyme immunoassay CV Coefficient of variation

Management and monitoring of hyperthyroid cats: a survey of Australian veterinarians

“…Hypertension is present in 14 to 23% of hyperthyroid cats at diagnosis, though has been reported in up to 87% of cats in one study, and importantly, 23% of initially normotensive cats develop hypertension following restoration of euthyroidism. [30][31][32] Hypertension has been correlated with reduced survival times in a retrospective study of cats treated primarily with anti-thyroid medications and/or thyroidectomy. 33 Practice policies for management of feline hyperthyroidism were reported by approximately one-quarter of veterinarians in our survey.…”