Inter-observer variation in the diagnosis of neurologic abnormalities in the horse

Authors: SAVILLE, WILLIAM - The Ohio State University; REED, STEVEN - Rood And Riddle Equine Hospital; Dubey, Jitender; GRANSTROM, DAVID - Veterinary Medical Association; MORLEY, PAUL - Colorado School Of Public Health; HINCHCLIFF, KENNETH - University Of Melbourne; KOHN, CATHERINE - The Ohio State University; WITTUM, THOMAS - The Ohio State University; WORKMAN, JEFFREY - The Ohio State University

Submitted to: Journal of Veterinary Internal Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2017
Publication Date: 9/9/2017
Citation: Saville, W., Reed, S., Dubey, J.P., Granstrom, D., Morley, P., Hinchcliff, K., Kohn, C., Wittum, T., Workman, J. 2017. Inter-observer variation in the diagnosis of neurologic abnormalities in the horse. Journal of Veterinary Internal Medicine. 1:1871–1876. https://doi.org/10.1111/jvim.14822.
DOI: https://doi.org/10.1111/jvim.14822

Interpretive Summary: Toxoplasma and Sarcocystis are related single celled parasites of livestock and humans. While Toxoplasma has long been recognized to cause neurologic disease in many warm blooded hosts, including humans, parasites in the related genus Sarcocystis also cause serious disease in livestock and even in humans. Sarcocystis neurona causes a fatal neurological disease in horses called Equine Protozoal Myeloencephalitis (EPM) in Americas. Facial nerve paralysis, muscular atrophy, and limb abnormalities are the most common clinical signs of EPM. In the present study, the authors present data concerning good agreement between recognition of clinical signs in horses by different attending veterinarians.These results will be of interest to veterinarians, parasitologists, and horse owners.

Technical Abstract: Background – The diagnosis of EPM relies heavily on the clinical examination. The accurate identification of neurologic signs during a clinical examination is critical to the interpretation of laboratory results. Objective – To investigate the level of agreement between board-certified veterinary internists when performing neurologic examinations in horses. Animals – Consisted of 97 horses admitted to the Veterinary Teaching Hospital at The Ohio State University from December 1997 to June 1998. Methods – A prospective epidemiologic research design was used. Horses enrolled in the study were examined by the internist responsible for care of the horse and later by an internist that was not aware of the presenting complaint or other patient history. Data were analyzed using descriptive statistics, and kappa (K) statistics were calculated to assess inter-observer agreement. Results – A total of 97 horses were enrolled in the study. Overall, examiners agreed that 60/97 (61.9%) were clinically abnormal, 21/97 (21.6%) were clinically normal, and the status of 16.5% of horses was contested. There was complete agreement among the examiners with regard to cranial nerve signs and involuntary movements. Disagreement involving severity of clinical signs occurred in 31 horses, and 25 of those horses (80.6%) were considered either normal or mildly affected by the primary observer. When examining the results of all paired clinical examinations for eleven different categories, there was wide variability in the results. When examiners rated the presence or absence of any neurologic abnormalities, lameness, or ataxia, the agreement between observers was either good or excellent for 80% of horses. When assessing truncal sway, the agreement between observers was good or excellent for 60% of the horses. When examining the horses for asymmetry of deficits or weakness, agreement was either good or excellent for 40% of the horses. Agreement between observers was excellent or good for only 20% of the horses when assessing muscle atrophy, spasticity and overall assessment of the severity of neurologic abnormalities. Conclusions and clinical importance – This study underscores the subjectivity of the neurologic examinations and demonstrates a reasonable level of agreement that may be achieved when different clinicians examine the same horse.