Factors associated with concordant and discordant interpretations

Outcome events

The overall event rate among stress echocardiogram patients in the PROMISE trial \cite{disease2015}was low. In the small number of SE patients who had a clinical outcome, those with discordant SE results were more likely to undergo referral for a second non-invasive test or coronary angiography. A discordant stress echo result was not associated with 90-day revascularization, cardiovascular death, myocardial infarction, all-cause death, and hospitalization for unstable angina.

Discussion

Our study showed that among outpatients with chest pain who underwent stress echocardiography for risk stratification, agreement between between site and core lab interpretation was poor, with positive results according to site interpretation that were normal according to core lab interpretation. Predictors of discrepancy between site and core lab interpretations were. 
A substudy of the Global Registry of Acute Coronary Events (GRACE) registry found significant and clinically important discrepancies in local site and core laboratory interpretation of electrocardiograms in acute coronary syndrome patients \cite{Yan_2007}. Previous studies have shown that echocardiographer experience contributes to the diagnostic accuracy of stress echocardiogram interpretation and accuracy of interpretation improves with adequate training \cite{Picano_1991}. A smaller substudy of the ISCHEMIA trial \cite{health2015} cohort found agreement between local site and core lab interpretation of myocardial ischemia by stress echocardiogram in 81% of cases and similar for both exercise and pharmacologic stress tests. In cases of disagreement, the majority were adjudicated as no or mild ischemia by the core lab and more extensive ischemia by the local site \cite{Kataoka_2015}. A multicenter study using stress echocardiograms from six institutions found an average kappa coefficient of 0.48 between institutions and percentage agreement was highest in cases of three-vessel disease or left anterior descending artery disease \cite{Peteiro_2006} (agreement lower when blinded? Go back and read the discussion).
In a small prospective study, interpretation of dobutamine stress echocardiography has been found to be affected by low image quality, a wall motion abnormality which is not severe, and a low peak rate-pressure product resulting in low inter-rater agreement \cite{Hoffmann1998}.
Cognitive bias due to presence of clinical information at site whereas this was not available to the core lab.
Harmonic imaging has also improved interpreter agreement and studies with poor image quality have previously been noted to have more inter-observer variability \cite{Hoffmann_2002}.
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