Focused cardiac ultrasonography's diagnostic potential limited by low specificity

Focused cardiac ultrasonography (FoCUS) may be more useful for ruling out significant cardiovascular pathology in patients at low suspicion of disease than for confirming cardiovascular disease when it is strongly suspected, a study found.

Researchers reviewed nine published studies to compare the accuracy of FoCUS-assisted clinical assessment versus clinical assessment alone for diagnosing left ventricular dysfunction (defined as left ventricular ejection fraction <50%) or valvular disease. Findings from the systematic review and meta-analysis were published Aug. 6 by Annals of Internal Medicine.

FoCUS yielded significantly greater sensitivity, but not greater specificity, than clinical assessment alone, the study found. The sensitivity of clinical assessment for diagnosing left ventricular dysfunction was 43% (95% CI, 33% to 54%), and with FoCUS-assisted examination, it was 84% (95% CI, 74% to 91%). The specificity of clinical assessment was 81% (95% CI, 65% to 90%) compared to 89% (95% CI, 85% to 91%) with FoCUS. The sensitivities of clinical assessment and FoCUS-assisted examination for diagnosing aortic or mitral valve disease of at least moderate severity were 46% (95% CI, 35% to 58%) and 71% (95% CI, 63% to 79%), respectively. Both clinical assessment and FoCUS-assisted examination had a specificity of 94% (95% CI, 91% to 96%) for this outcome.

The study authors concluded that FoCUS may be better for ruling out clinically significant cardiovascular pathology in patients at low suspicion of disease than for confirming suspected cardiovascular disease. Clinicians must understand the situations where formal echocardiography should be used and the inherent limitations of FoCUS in terms of both image acquisition and interpretation before using it in practice, they said.

An editorial added that hand-held ultrasonography could be the fifth pillar of the physical examination and improve the accuracy of bedside diagnosis but cautioned that its effectiveness is limited by the skills and expertise of the clinician. The editorialists suggested that incorporating hand-held ultrasonography in primary care, where most echocardiograms are ordered, could greatly improve downstream workup and cost-effectiveness.

“After more than 2 centuries of using the stethoscope (sound) as the primary tool for bedside cardiac diagnosis, hand-held devices (ultrasound) are an exciting addition to the cardiac examination—but they are not without challenges related to proficiency, operator dependency, and cost,” the editorial said. “With the advent of imaging, ‘seeing is believing,’ but the truth depends on the skills and expertise of the beholder.”