Statistical Analysis
Vscan assessments made by the outpatient providers were compared to those made by the blinded expert echocardiography readers. Discordance between the two readers was considered when disagreement in diagnoses of significant abnormality was found. Kappa coefficients (κ) were calculated as the degree of agreement between the two p-values <0.05 were considered significant.
Kappa coefficients above 0.90 were considered identical or nearly identical in their agreement, 0.80-0.90 were considered a strong level of agreement, 0.60-0.79 as moderate, and 0.40-0.59 weak.
The study was powered based on Kappa agreements of the two variables: (i) Accuracy of valve disease severity grading (none, mild, moderate/severe) (ii) Accuracy of grading of ejection fraction (none, mild, moderate/severe) and assumes the proportion of patients that fall into each of these groups will be equally distributed at one-third. Power analyses were carried out for agreement levels (alternate hypothesis) of 0.9 and 0.8 compared to baseline (null hypothesis) levels of 0.6 and 0.7 at sample sizes of 100 to 500 incremented by 50 with a two-sided alpha of 0.05. Because of the large volume of echocardiograms performed at Abbott Northwestern Hospital, the investigators believe we should use a sample size of 350, which achieves a power of 0.91 to detect a true Kappa value of 0.80 (alternate hypothesis) in a test of H0: Kappa = 0.70.