Interobserver agreement during clinical magnetic resonance imaging of the equine foot.

ABSTRACT

BACKGROUND: Agreement between experienced observers for assessment of pathology and assessment confidence are poorly documented for magnetic resonance imaging (MRI) of the equine foot. OBJECTIVES: To report interobserver agreement for pathology assessment and observer confidence for key anatomical structures of the equine foot during MRI. STUDY DESIGN: Exploratory clinical study. METHODS: Ten experienced observers (diploma or associate level) assessed 15 equine foot MRI studies acquired from clinical databases of 3 MRI systems. Observers graded pathology in seven key anatomical structures (Grade 1 no pathology, Grade 2 mild pathology, Grade 3 moderate pathology, Grade 4 severe pathology) and provided a grade for their confidence for each pathology assessment (Grade 1 high confidence, Grade 2 moderate confidence, Grade 3 limited confidence, Grade 4 no confidence). Interobserver agreement for the presence/absence of pathology and agreement for individual grades of pathology were assessed with Fleiss' kappa (k). Overall interobserver agreement for pathology was determined using Fleiss' kappa and Kendall's coefficient of concordance (KCC). The distribution of grading was also visualised with bubble charts. RESULTS: Interobserver agreement for the presence/absence of pathology of individual anatomical structures was poor-to-fair, except for the navicular bone which had moderate agreement (k = 0.52). Relative agreement for pathology grading (accounting for the ranking of grades) ranged from KCC = 0.19 for the distal interphalangeal joint to KCC = 0.70 for the navicular bone. Agreement was generally greatest at the extremes of pathology. Observer confidence in pathology assessment was generally moderate to high. MAIN LIMITATIONS: Distribution of pathology varied between anatomical structures due to random selection of clinical MRI studies. Observers had most experience with low-field MRI. CONCLUSIONS: Even with experienced observers, there can be notable variation in the perceived severity of foot pathology on MRI for individual cases, which could be important in a clinical context.