Predictors of laminitis development in a cohort of nonlaminitic ponies

BACKGROUND: Quantifying risk factors for laminitis development requires improvement. OBJECTIVES: To identify the most useful physical examination, metabolic and management factors to predict laminitis development in client‐owned, nonlaminitic ponies. STUDY DESIGN: Prospective cohort study. METHODS: Physical examination, metabolic and management data were collected from a pony cohort 6 monthly for up to 4 years. Ponies were monitored for the development of laminitis. Metabolic data included basal plasma concentrations of ACTH ([ACTH]), adiponectin ([adiponectin]), triglycerides and glucose. Serum insulin concentrations ([insulin]) were measured in the unfasted basal state ([insulin]T0) and 60 minutes ([insulin]T60) after administration of corn syrup (0.3ml/kg). Separate multivariable Cox proportional‐hazards models were developed for physical, management/signalment and metabolic data and later combined into two final models. Low‐, medium‐ and high‐laminitis risk categories were defined based on basal or T60 [insulin]. RESULTS: Overall, 374 ponies (age 5‐32 years) and 891 pony‐years were included in the main analysis. Laminitis incidence (95% confidence interval (CI)) was 4.8 (3.5‐6.5) cases/100 pony‐years. Laminitis development was associated with numerous univariable factors. Significant (P < .05) factors retained in the final multivariable models included [insulin]T0, [insulin]T60, [adiponectin] and divergent hoof growth. [ACTH] was not independently associated with laminitis. Based on [Insulin]T0, low‐ (<21.6 µIU/ml), medium‐ (21.6‐45.2 µIU/ml) and high‐risk (>45.2 µIU/ml) categories encompassed 70, 20 and 10% of the population and had estimated 4‐year laminitis incidences (95%CI) of 6 (2‐9)%, 22 (10‐33)% and 69 (48‐82)% respectively. Based on [Insulin]T60 the low‐ (<53.4 µIU/ml), medium‐ (53.4‐153 µIU/ml) and high‐risk (≥153 µIU/ml) categories comprised 60, 30 and 10% of the population and had estimated 4‐year laminitis incidences (95%CI) of 3 (0‐6)%, 20 (10‐29)% and 73 (52‐84)% respectively. MAIN LIMITATIONS: Results may not apply to different insulin assays, geographical regions, breeds or management types. CONCLUSIONS: [Insulin]T0 or [insulin]T60 best quantify the risk of future laminitis development in nonlaminitic ponies.