Scientist Zomedica Ann Arbor, Michigan, United States
Abstract:
Background: Hypothyroidism is commonly diagnosed in dogs. In addition to evaluating an animal’s clinical signs, measurement of endogenous thyroid molecules – including total thyroxine (tT4), thyroid-stimulating hormone (TSH), and free thyroxine (fT4) - frequently aids in identifying hypothyroid animals. In-clinic tT4 and TSH tests are available but a point-of-care (POC) fT4 assay with accurate measurements is needed, especially since approximately 25% of hypothyroid dogs do not have elevated TSH levels.
Objective: Assess the diagnostic performance of canine POC fT4 measurements for identifying hypothyroidism.
Animals: 66 canines believed to be euthyroid (n = 28) or suspected of having hypothyroidism (n = 38) based on clinical and clinicopathologic signs from across four American veterinary clinics.
Methods: All animals underwent a physical exam and screening workup, including complete blood count, chemistry, urinalysis, and thyroid diagnostic profile, performed at a reference lab. In addition, serum tT4, TSH, and fT4 levels were measured in-clinic on the TRUFORMA® diagnostic platform. Blinded to TRUFORMA results, a board-certified endocrinologist diagnosed the animals based on the reference lab results and their clinical and clinicopathologic signs.
Results: The clinical sensitivity of the TRUFORMA fT4 assay was 100% (95% CI: 46.3 – 100%) while the specificity was 88.5% (77.2 – 94.9%) when compared to the final endocrinologist diagnosis. Factoring in additional TRUFORMA results (tT4 and/or TSH) led to even higher clinical specificity with a maximum of 96.7% (95% CI: 87.6 – 99.4%) being achieved.
Conclusion: The TRUFORMA point-of-care fT4 assay can aid in distinguishing hypothyroid dogs from those that are euthyroid.
