Abstract
BackgroundDiseases associated with insulin dysregulation (ID), such as equine metabolic syndrome and pituitary pars intermedia dysfunction, are of interest to practitioners because of their association with laminitis. Accurate insulin concentration assessment is critical in diagnosing and managing these diseases.Hypothesis/ObjectivesTo determine the effect of time, temperature, and collection tube type on insulin concentrations in horses at risk of ID.AnimalsEight adult horses with body condition score >6/9.MethodsIn this prospective study, subjects underwent an infeed oral glucose test 2 hours before blood collection. Blood samples were divided into ethylenediaminetetraacetic acid, heparinized, or serum tubes and stored at 4 or 20°C. Tubes were centrifuged and analyzed for insulin by a chemiluminescent assay over 8 days. Changes in insulin concentrations were compared with a linear mixed effects model.ResultsAn overall effect of time, tube type and temperature was identified (P = .01, P = 0.001, and P = 0.001, respectively). Serum and heparinized samples had similar concentrations for 3 days at 20°C and 8 days at 4°C; however, after 3 days at 20°C, heparinized samples had significantly higher insulin concentrations (P = .004, P = .03, and P = .03 on consecutive days). Ethylenediaminetetraacetic acid samples had significantly lower insulin concentrations regardless of time and temperature (P = .001 for all comparisons).Conclusions and Clinical ImportanceThese results suggest an ideal protocol to determine insulin concentrations involves using serum or heparinized samples with analysis occurring within 3 days at 20°C or 8 days at 4°C.
Highlights
An aging equine population and increased prevalence of obesity together with a better understanding of equine endocrine disorders have led to a rise in the recognition of endocrinopathies in horses.[1-3]
At 4C, there was no significant difference in immunoreactive insulin concentrations between serum and heparinized samples at any time point and the median concentrations were close to their assay coefficients of variation
Our findings indicate that immunoreactive insulin concentrations in both serum and heparinized plasma remain stable up to 8 days when stored at 4C, and up to 3 days when stored at 20C
Summary
An aging equine population and increased prevalence of obesity together with a better understanding of equine endocrine disorders have led to a rise in the recognition of endocrinopathies in horses.[1-3]. As excessive insulin concentrations have been associated with an increased risk of developing laminitis, an accurate diagnosis of ID is critical for ensuring optimal patient health and welfare outcomes.[7,8]. Diseases associated with insulin dysregulation (ID), such as equine metabolic syndrome and pituitary pars intermedia dysfunction, are of interest to practitioners because of their association with laminitis. Hypothesis/Objectives: To determine the effect of time, temperature, and collection tube type on insulin concentrations in horses at risk of ID. Ethylenediaminetetraacetic acid samples had significantly lower insulin concentrations regardless of time and temperature (P = .001 for all comparisons). Conclusions and Clinical Importance: These results suggest an ideal protocol to determine insulin concentrations involves using serum or heparinized samples with analysis occurring within 3 days at 20C or 8 days at 4C
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