Abstract: The prevalence of insulin dysregulation (ID) has not been investigated in sport horses. Stall-side insulin assays offer convenience but need further validation. Objective: To determine the prevalence of and risk factors for ID in a sport horse population using an oral sugar test (OST) and assess agreement between stall-side and validated laboratory assays for insulin quantification. Methods: Prospective cross-sectional study. Methods: One hundred eighty sport horses presenting for orthopaedic evaluation at a university hospital (N = 140) or local farms (N = 40) were tested for ID using OST (0.15 mL/kg light corn syrup). Morphometric data were collected, and baseline serum leptin and adiponectin concentrations were measured. Insulin concentrations were measured using the validated fluorescence enzyme immunoassay (FEIA) and a stall-side lateral flow assay (LFA). ID was diagnosed if FEIA insulin measured >20 μIU/mL at T0 or >30 μIU/mL at T60/T90. Factors associated with ID were assessed using a mixed effects binary logistic regression model. Assay agreement was assessed using Pearson's correlation coefficient and Bland-Altman plot. Receiver operator characteristic curve analysis was performed to determine diagnostic cut-offs for LFA. Results: ID was diagnosed in 22.8% (41/180) of horses. Only 11/41 ID horses had increased fasted insulin. Increasing leptin/adiponectin ratio in males was the only significant predictor of ID (OR = 1.102, 95% CI 1.036-1.171). Correlation between FEIA and LFA insulin measures was good (r = 0.81, 95% CI 0.78-0.84), but the LFA read on average 13.62 μIU/mL higher than the FEIA and had greater variability at higher insulin concentrations. Area under the ROC curve showed the LFA was excellent at correctly classifying ID status (AUC = 0.95, 95% CI 0.93-0.97). Conclusions: Single-centre study, voluntary enrolment may overestimate ID prevalence. Conclusions: ID is common in sport horses and often requires dynamic insulin testing to diagnose. Physical appearance does not predict ID risk. Agreement between stall-side and laboratory assays is good. INTRODUÇÃO: A prevalência de desregulação da insulina (DI) não foi investigada em cavalos atletas. Ensaios de insulina realizados a campo oferecem praticidade, mas necessitam de maior validação. Objective: Determinar a prevalência e os fatores de risco para DI em uma população de cavalos atletas utilizando o teste oral de açúcar (TOA), e avaliar a concordância entre ensaios de insulina realizados a campo e métodos laboratoriais validados para quantificação de insulina. Unassigned: Estudo transversal prospectivo. MÉTODOS: Cento e oitenta cavalos atletas atendidos para avaliação ortopédica em um hospital universitário (N = 140) ou em propriedades locais (N = 40) foram testados para DI utilizando TOA (0,15 mL/kg de xarope de milho claro). Dados morfométricos foram coletados, e as concentrações séricas basais de leptina e adiponectina foram mensuradas. As concentrações de insulina foram determinadas por meio de um imunoensaio enzimático fluorescente validado (FEIA) e de um ensaio de fluxo lateral realizado a campo (LFA). A DI foi diagnosticada quando a insulina medida por FEIA foi >20 μIU/mL em T0 ou >30 μIU/mL em T60/T90. Fatores associados à DI foram avaliados por meio de um modelo de regressão logística binária com efeitos mistos. A concordância entre os ensaios foi avaliada pelo coeficiente de correlação de Pearson e pelo gráfico de Bland‐Altman. A análise da curva ROC foi realizada para determinar pontos de corte diagnósticos para o LFA. Results: A DI foi diagnosticada em 22,8% (41/180) dos cavalos. Apenas 11/41 cavalos com DI apresentaram insulina elevada em jejum. O aumento da razão leptina/adiponectina em machos foi o único preditor significativo de DI (OR = 1,102; IC 95%: 1,036–1,171). A correlação entre as medidas de insulina por FEIA e LFA foi boa (r = 0,81; IC 95%: 0,78–0,84), porém o LFA apresentou, em média, valores 13,62 μIU/mL mais altos que o FEIA e maior variabilidade em concentrações elevadas de insulina. A área sob a curva ROC demonstrou que o LFA apresentou excelente desempenho na classificação correta do status de DI (AUC = 0,95; IC 95%: 0,93–0,97). PRINCIPAIS LIMITAÇÕES: Estudo de centro único; o recrutamento voluntário pode superestimar a prevalência de DI. CONCLUSÕES: A DI é comum em cavalos atletas e frequentemente requer testes dinâmicos de insulina para o diagnóstico. A aparência física não prediz o risco de DI. A concordância entre ensaios realizados a campo e laboratoriais é boa.
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Overview
This study examined how common insulin dysregulation (ID) is in sport horses and identified risk factors using a specialized oral sugar test (OST).
Additionally, it compared the accuracy of a quick stall-side insulin test with a validated laboratory method.
Study Purpose and Background
Insulin dysregulation (ID) is a condition related to abnormal insulin levels, important in horse health but not well studied in sport horses.
Traditional laboratory insulin assays are reliable but slow, while stall-side (field) tests provide quick results but need validation.
The study aimed to:
Determine how common ID is in sport horses
Identify risk factors associated with ID
Evaluate agreement between the rapid stall-side insulin test and a validated lab assay
Methods
Design:
Prospective, cross-sectional study
Conducted at a university hospital and local farms
Subjects:
180 sport horses undergoing orthopedic evaluation (140 hospital, 40 farms)
Testing protocol:
Oral Sugar Test (OST) with light corn syrup given at 0.15 mL/kg
Blood samples taken at baseline (fasting, T0) and timed intervals after sugar administration (T60, T90)
Serum leptin and adiponectin levels also measured as metabolic markers
Physical data (morphometrics) collected for each horse
Diagnostic criteria for ID:
FEIA insulin >20 μIU/mL at baseline (T0) or >30 μIU/mL at T60 or T90 defined presence of ID
Statistical analyses:
Logistic regression to identify factors predicting ID
Correlation and Bland-Altman analyses to assess agreement between LFA and FEIA insulin results
Receiver operating characteristic (ROC) curve to evaluate stall-side test diagnostic accuracy and determine cut-off values
Key Findings
Prevalence:
22.8% of sport horses (41 out of 180) tested positive for insulin dysregulation by OST
Only 11 of these had elevated fasting insulin, showing that dynamic testing (OST) detects more cases than fasting insulin alone
Risk factors:
Physical appearance and morphometric data did not predict ID risk; body condition was not a reliable indicator
In male horses, an increased leptin/adiponectin ratio was a significant predictor for ID (Odds Ratio 1.102)
Stall-side test (LFA) performance:
Good correlation with lab FEIA insulin measurements (r = 0.81)
LFA tended to read on average 13.62 μIU/mL higher than FEIA, especially at higher insulin levels
Greater variability observed with LFA at higher insulin concentrations
ROC curve analysis showed excellent diagnostic accuracy for the LFA test (AUC 0.95), indicating it can effectively classify ID status
Conclusions and Implications
Insulin dysregulation is relatively common in sport horses, occurring in nearly one-quarter of tested individuals.
Dynamic testing using OST is necessary to accurately identify ID as fasting insulin alone misses many cases.
Physical characteristics and body condition are poor predictors of insulin dysregulation risk, suggesting veterinarians should not rely on appearance.
The stall-side lateral flow assay shows good agreement with validated lab measures and can be a useful rapid diagnostic tool, though it tends to overestimate insulin at higher levels.
Further validation, particularly in larger and more diverse populations, is warranted to confirm these findings.
Study Limitations
Single-center study setting may limit generalizability to all sport horse populations.
Voluntary enrollment could have led to overestimation of the true prevalence of ID due to selection bias.
More research needed to refine stall-side test interpretation at higher insulin values.
Cite This Article
APA
Hallowell KL, Horne CR, Miller CS, Tufts SR, Dembek K, Love KR, van Eps AW, Schnabel LV.
(2026).
Prevalence of insulin dysregulation in a sport horse population as determined by traditional and stall-side testing.
Equine Vet J.
https://doi.org/10.1002/evj.70204
Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.
Horne, Caitlyn R
Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.
Miller, Cary S
Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.
Tufts, Sara R
Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.
Dembek, Katarzyna
Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.
Love, Kim R
K. R. Love Quantitative Consulting and Collaboration, Athens, Georgia, USA.
van Eps, Andrew W
Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, Pennsylvania, USA.
Schnabel, Lauren V
Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, Raleigh, North Carolina, USA.
Comparative Medicine Institute, North Carolina State University, Raleigh, North Carolina, USA.
Grant Funding
Foundation for the Horse
T32OD011130 / NIH HHS
Herbert Benjamin Endowment
FORGE - Fund for Orthopedic Research in honor of Gus and Equine athletes
Wellness Ready
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