Evaluation of the diagnostic accuracy of skeletal scintigraphy in lame and poorly performing sports horses.

Skeletal scintigraphy is an established imaging modality, however, its validity as a diagnostic test in lame or poorly performing sports horses has not been determined. The objective of this retrospective cross-sectional analytical study was to determine the accuracy of skeletal scintigraphy as an indiscriminate screening test in sports horses. All sports horses that underwent scintigraphic examination between March 2008 and December 2014 for which a definitive diagnosis was reached were included. Examinations were evaluated blindly. Characteristics of increased radiopharmaceutical uptake were recorded and subjectively categorized as possibly relevant or non-relevant. Kappa statistics were used to assess agreement between test results and final diagnosis. There were 1222 positive clinical diagnoses in 480 horses, of which 687 regions (56.4%) had no associated increased radiopharmaceutical uptake and 99 regions (8.1%) had non-relevant increased radiopharmaceutical uptake. The sensitivity of increased radiopharmaceutical uptake for identification of final diagnosis was low (43.8%) and specificity was high (94.0%). The agreement was fair (κ = 0.36). Relevance categorization improved the test; the sensitivity for final diagnosis was low (35.7%), specificity was high (98.9%), and the agreement was moderate (κ = 0.45). The agreements of increased radiopharmaceutical uptake and relevance categorization with final diagnosis were only substantial for feet (κ = 0.67 and κ = 0.66, respectively) and proximal aspect of the forelimb (elbow, shoulder, and scapula combined) (κ = 0.69 and 0.78, respectively). Scintigraphic examination is unlikely to lead to a full and correct diagnosis of the cause(s) of lameness or poor performance in sports horses when used as an isolated or indiscriminate screening tool.