ObjectivesA thyrotropin (TSH) assay using bulk acoustic wave technology (TSH-BAW) was recently developed that allows for more accurate differentiation of euthyroid and hyperthyroid cats compared to the currently available TSH chemiluminescent assay (TSH-CLIA). The TSH-BAW is a highly sensitive and specific test for diagnosing hyperthyroidism; however, the effect of nonthyroidal illness (NTI) on this assay aside from cats with chronic kidney disease has not been evaluated. Primary objectives of this study were to compare serum TSH concentrations using both assays in hyperthyroid cats, cats with NTI, and healthy cats, and to evaluate the sensitivity and specificity of the TSH-BAW for diagnosing hyperthyroidism.MethodsProspective cross-sectional study comparing the TSH concentration of hyperthyroid, healthy, and euthyroid sick cats using the TSH-CLIA and TSH-BAW assays. The effect of disease severity was evaluated with hyperthyroidism and NTI.ResultsThe sensitivity and specificity of TSH-BAW for detecting hyperthyroidism were 78% [95% CI 62-90%] and 97% [95% CI 84-100%], respectively. The median serum TSH concentration was significantly different between hyperthyroid cats compared to healthy and NTI cats with both assays (P<0.01), but was not different between the latter euthyroid groups (TSH-CLIA P=0.168, TSH-BAW P=0.673). Eight (8/37; 21.6%) hyperthyroid cats had a detectable TSH-BAW but undetectable TSH-CLIA. The TSH-BAW concentrations were not significantly different between severities of NTI (P=0.565).Conclusions and relevanceThe TSH-BAW has a high specificity for detecting hyperthyroidism and is not significantly affected by NTI. While it is a useful assay for diagnosing hyperthyroidism, a normal TSH-BAW result cannot rule it out.
Keywords: Bulk acoustic wave (BAW); Feline TSH; Feline thyrotropin; Hyperthyroidism.