Informed Hypothetico‐Deductive Reasoning Based on Clinical Signs for Diagnosis of Equine Laminitis Using Decision Tree Analysis

Abstract

Reasons for performing study Effective diagnosis of equine laminitis is necessary to allow prompt instigation of palliative and therapeutic treatments, yet there has been limited work regarding diagnostic accuracy. Objectives To compare the prevalence of clinical signs in laminitis and non‐laminitis lamenesses to evaluate the capabilities of discrimination for differential diagnosis. Study design Analytical epidemiological study. Methods Veterinary practitioners completed a pre‐designed checklist of laminitis‐associated clinical signs identified by literature review, for equine lameness of any origin. A case was defined as a horse/pony with veterinary‐diagnosed, clinically apparent laminitis, attended by a participating practitioner. Associations between clinical signs and case/control status were tested by logistic regression with adjusted odds ratios and 95% confidence intervals, with veterinary practice as a fixed effect, and Wald P‐value calculated. Multivariable analysis using graphical classification tree‐based statistical models allowed comprehension of the prevalence in the data associated with particular clusters of clinical signs. Results Data were collected for 588 laminitis cases and 201 non‐laminitis lamenesses. The overall prevalence of specific clinical signs ranged from 2.7% for ‘sole prolapse’ to 85.0% for ‘lame at trot’. Differences in prevalence ranged from −14.1% for ‘lame at trot’ (more common in controls) to +71.9% for ‘short stilted gait at walk’ (more common in cases). Five clinical signs had a difference in prevalence of greater than +50%: ‘reluctance to walk’, ‘short, stilted gait at walk’, ‘difficulty turning’, ‘shifting weight’ and ‘increased digital pulse’. Bilateral forelimb lameness was the best discriminator (92% of animals with this clinical sign had laminitis). The additional presence of increased digital pulses improved this to 99%. Flat/convex sole, shifting weight and short stilted gait at walk were also useful discriminators. Conclusions This is the first study to provide information aiding diagnostic hypothetico‐deductive reasoning based on clinical signs to differentially diagnose laminitis from other lamenesses. Ethical animal research: Ethical approval obtained from Royal Veterinary College. Owners gave informed consent for their horses' inclusion in the study. Sources of funding: Project funded by World Horse Welfare. C . E . W ylie currently funded by The Margaret Giffen Charitable Trust. Competing interests: None declared.