Thus, the study population represented a heterogeneous mix of patients. Others studies were eliminated because of methodological flaws. This meta-analysis is well done. They also performed a sensitivity analysis that showed that these data are robust. The main limitation to this study is the question of external validity.
Echocardiography is highly operator dependent.
The results found in a study situation, where echocardiographers have a particular interest in echocardiography, may not reflect the level of expertise with echocardiography available to most physicians. Thus, the sensitivity and specificity of echocardiography may be lower in the community setting than in the study setting. This is called a post-test referral or validation bias. This advantage of echocardiography held true in all subgroups. It is likely that this result will vary somewhat depending on the skill available in the community with each technique.