Clinical assessment of transthoracic echocardiography skills: a generalizability study

Transthoracic echocardiography (TTE) is a widely used cardiac imaging technique that all cardiologists should be able to perform competently. Traditionally, TTE competence has been assessed by unstructured observation or in test situations separated from daily clinical practice. An instrument for assessment of clinical TTE technical proficiency including a global rating score and a checklist score has previously shown reliability and validity in a standardised setting. As clinical test situations typically have several sources of error giving rise to variance in scores, a more thorough examination of the generalizability of the assessment instrument is needed.

Nine physicians performed a TTE scan on the same three patients. Then, two raters rated all 27 TTE scans using the TTE technical assessment instrument in a fully crossed, all random generalizability study. Estimated variance components were calculated for both the global rating and checklist scores. Finally, dependability (phi) coefficients were also calculated for both outcomes in a decision study.

For global rating scores, 66.6% of score variance can be ascribed to true differences in performance. For checklist scores this was 88.8%. The difference was primarily due to physician-rater interaction. Four random cases rated by one random rater resulted in a phi value of 0.81 for global ratings and two random cases rated by one random rater showed a phi value of 0.92 for checklist scores.

Using the TTE checklist as opposed to the TTE global rating score had the effect of minimising the largest source of error variance in test scores. Two cases rated by one rater using the TTE checklist are sufficiently reliable for high stakes examinations. As global rating is less time consuming it could be considered performing four global rating assessments in addition to the checklist assessments to account for both reliability and content validity of the assessment.