Evaluation of Four Diagnostic Tests for Insulin Dysregulation in Adult Light‐Breed Horses

Abstract

BackgroundSeveral tests have been evaluated in horses for quantifying insulin dysregulation to support a diagnosis of equine metabolic syndrome. Comparing the performance of these tests in the same horses will provide clarification of their accuracy in the diagnosis of equine insulin dysregulation.ObjectivesThe aim of this study was to evaluate the agreement between basal serum insulin concentrations (BIC), the oral sugar test (OST), the combined glucose‐insulin test (CGIT), and the frequently sampled insulin‐modified intravenous glucose tolerance test (FSIGTT).AnimalsTwelve healthy, light‐breed horses.MethodsRandomized, prospective study. Each of the above tests was performed on 12 horses.ResultsMinimal model analysis of the FSIGTT was considered the reference standard and classified 7 horses as insulin resistant (IR) and 5 as insulin sensitive (IS). In contrast, BIC and OST assessment using conventional cut‐off values classified all horses as IS. Kappa coefficients, measuring agreement among BIC, OST, CGIT, and FSIGTT were poor to fair. Sensitivity of the CGIT (positive phase duration of the glucose curve >45 minutes) was 85.7% and specificity was 40%, whereas CGIT ([insulin]45 >100 μIU/mL) sensitivity and specificity were 28.5% and 100%, respectively. Area under the glucose curve (AUC g0‐120) was significantly correlated among the OST, CGIT, and FSIGTT, but Bland–Altman method and Lin's concordance coefficient showed a lack of agreement.ConclusionsCurrent criteria for diagnosis of insulin resistance using BIC and the OST are highly specific but lack sensitivity. The CGIT displayed better sensitivity and specificity, but modifications may be necessary to improve agreement with minimal model analysis.

<b>Avaliação da frutosamina em cavalos com e sem resistência à insulina</b>

“…O efeito biológico da insulina só é alcançado quando determinado número de receptores estiverem ocupados. Caso estes receptores não estejam funcionais, são necessárias maiores concentrações de insulina para que se atinja o efeito biológico, caracterizando desta forma a resistência à insulina ou a insensibilidade à insulina (DUNBAR et al, 2016).…”

“…Os animais resistentes à insulina respondem de maneira mais lenta a redução da glicemia ou, ainda, não atingem o nível de 50% do valor basal, além de ter um retorno aos valores iniciais mais rápido que os animais saudáveis (COELHO et al, 2011;DUNBAR et al, 2016).…”

“…São considerados resistentes à insulina animais que apresentem valores de insulina superiores a 60 µU/ml aos 75 minutos (FRANK, 2011;DUNBAR et al, 2016).…”

“…Apesar de não obter valores sob condições fisiológicas, por ser um teste de desafio, é um teste objetivo capaz de avaliar a RI tecidual (FIRSHMAN;VALBERG, 2007;DUNBAR et al, 2016).…”

“…O MMGI também apresentou boa correlação com o CHE em equinos, mas sua realização em situações clínicas é discutível por conta dos custos elevados relacionados principalmente à dosagem de insulina (CARSLAKE et al, 2016;DUNBAR et al, 2016).…”