Reader performance in radiographic diagnosis of signs of mitral regurgitation in cavalier King Charles spaniels

OBJECTIVES: To measure accuracy and variability of diagnosis by radiography of heart enlargement (HE) and heart failure (HF) in mitral regurgitation (MR). METHODS: Sixteen readers representing four levels of experience evaluated 50 sets of radiographs with varying severity of MR for presence or absence of HE, left atrial enlargement (LAE) and HF. The performance of the readers was compared with a reference standard, using area under the curve (AUC) of receiver operating characteristic (ROC) curves. The interreader agreement value kappa (K) was calculated. A subset of difficult cases of HF was analysed before and after removing an outlying reader from each group. RESULTS: AUC for HE was 0.89, for LAE it was 0.93 and for HF it was 0.92. Experience increased certainty of diagnosis but not accuracy. K ranges were HE, 0.53 to 0.67; LAE, 0.61 to 0.69 and HF, 0.49 to 0.58. When only difficult cases of HF were read, accuracy decreased and experienced readers performed better than inexperienced. When outlying readers were excluded, the differences between experienced and inexperienced readers increased. CLINICAL SIGNIFICANCE: LAE, not HE, should be used to evaluate the heart size and indirectly the severity of MR on radiographs. For HF, agreement among individual readers was only moderate. Studies of reader accuracy should consider the effects of interreader variability.