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Validation of a novel high-sensitivity radioimmunoassay procedure for measurement of total thyroxine concentration in psittacine birds and snakes

2001; American Veterinary Medical Association; Volume: 62; Issue: 11 Linguagem: Inglês

10.2460/ajvr.2001.62.1750

1943-5681

Cheryl B. Greenacre, Diane W. Young, Ellen N. Behrend, G. Heather Wilson,

Pesticide Residue Analysis and Safety

Abstract Objective —To validate a novel high-sensitivity radioimmunoassay (RIA) procedure developed to accurately measure the relatively low serum total thyroxine (T 4 ) concentrations of birds and reptiles and to establish initial reference ranges for T 4 concentration in selected species of psittacine birds and snakes. Animals —56 healthy nonmolting adult psittacine birds representing 6 species and 42 captive snakes representing 4 species. Procedure —A solid-phase RIA designed to measure free T 4 concentrations in dialysates of human serum samples was used without dialysis to evaluate total T 4 concentration in treated samples obtained from birds and reptiles. Serum T 4 binding components were removed to allow assay of undialyzed samples. Assay validation was assessed by determining recovery of expected amounts of T 4 in treated samples that were serially diluted or to which T 4 was added. Intra- and interassay coefficient of variation (CV) was determined. Results —Mean recovery of T 4 added at 4 concentrations ranged from 84.9 to 115.0% and 95.8 to 119.4% in snakes and birds, respectively. Intra- and interassay CV was 3.8 and 11.3%, respectively. Serum total T 4 concentrations for 5 species of birds ranged from 2.02 to 7.68 nmol/L but ranged from 3.17 to 142 nmol/L for blue-fronted Amazon parrots; concentrations ranged from 0.21 to 6.06 nmol/L for the 4 species of snakes. Conclusions and Clinical Relevance —This new RIA method provides a commercially available, accurate, and sensitive method for measurement of the relatively low serum T 4 concentrations of birds and snakes. Initial ranges for the species evaluated were established. ( Am J Vet Res 2001;62:1750–1767)