Point-of-Care Ultrasonography, Primary Care, and Prudence

A difficult to quantify, enthusiasm for diagnostic point-of-care ultrasonography (POCUS) in primary care seems to be substantial and growing (1). An increasing number of articles advocate for its use in primary care, and many internal medicine and family medicine residencies have plans to create POCUS curricula (2, 3). Recent statements of support for ultrasonography in internal medicine from the American College of Physicians and the Alliance for Academic Internal Medicine, as well as the development of an ultrasonography curriculum by the American Academy of Family Physicians, encourage the creation of these training programs and have likely furthered the embrace of this technology in primary care. Advocates of POCUS in this setting—mostly primary care clinicians aware of the limitations of the physical examination and the diagnostic tools available to them in their offices (4)—view it as a means to improve quality of care by increasing diagnostic accuracy; decreasing time to diagnosis; and decreasing costs through obviation of the need for further testing, imaging, and specialist evaluation (5). As its proponents point out, POCUS offers outpatient generalists and their patients many potential benefits; however, its integration into primary care warrants caution because primary care differs from other settings in important ways. Unlike in the emergency department and specialty clinics, data demonstrating the accuracy of POCUS in primary care remain wanting. For the most common uses of POCUS in primary care—obstetric, abdominal, and cardiac examination (1)—2 systematic reviews from 2019 identified just 3 unique studies assessing the accuracy of these examinations when done by primary care clinicians in primary care settings (1, 6). The first of these studies assessed both obstetric and abdominal examinations, the second evaluated the accuracy of estimates of left ventricular function, and the third evaluated the accuracy of broader cardiac examinations done by primary care clinicians. Unsurprisingly, the authors of both systematic reviews point out a need for future research. This future research ought to address not only accuracy of POCUS in primary care but also patient outcomes because such data remain scarce (4). It seems axiomatic that increased diagnostic accuracy produces better outcomes, but a study of patients with respiratory symptoms presenting to the emergency department calls this axiom into question. Although POCUS has superior accuracy to auscultation and chest radiography (7), the group evaluated with POCUS had no improvements in mortality or length of hospital stay but did receive more antibiotics than the control group assessed only with standard diagnostic techniques (8)— results that underscore the importance of outcomes data to clarify when POCUS benefits patients and when it leads to unnecessary medical care. Unfortunately, generalizing results from other settings to circumvent the lack of data for POCUS in primary care does not provide a satisfactory solution to the need for more studies. Sensitivities and specificities—and, consequently, likelihood ratios—depend on severity of disease (9). Because patients in the emergency department and specialty clinics tend to have more severe disease than those in primary care, extrapolations of these measures of accuracy require skepticism. In addition, extrapolating data from other settings assumes that examination quality is comparable between generalists and their colleagues—a doubtful assumption due to differences in training and prevalence of disease between settings. In contrast to other specialties that routinely use ultrasonography, internal medicine and family medicine have no ultrasonography requirements from the Accreditation Council for Graduate Medical Education, and a minority of residency programs have established ultrasonography curricula (2, 3). Although an abundance of courses exist that provide means for primary care clinicians to develop their POCUS skills (4), such courses typically do not provide the rigor of training that current recommendations consider necessary to attain competence to perform examinations without supervision (1). Until it becomes commonplace for primary care clinicians to receive such training, doubt will persist about the assumption that they are as skilled in ultrasonography examination as their colleagues. Moreover, because POCUS skills decay with time (10) and base rates of disease vary between clinical settings, concern also exists that primary care clinicians will not perform examinations as accurately as their colleagues when encountering pathology that they see infrequently. Finally, the differences in base rates of disease alter pretest probabilities and predictive value of diagnostic testing, further raising doubts about the external validity of data from disparate settings (6). In addition to concerns about accuracy, outcomes, and spectrum bias, primary care clinicians must also consider the feasibility of POCUS in their practice. Reasonable estimates suggest that scanning adds 5 to 10 minutes to a patient encounter (1), and changes to workflow raise concerns about financial sustainability. Although scanning can be billed using American Medical Association CPT (Current Procedural Terminology) codes, POCUS may not represent a financially feasible addition to a primary care clinician's practice if the clinician reduces appointments to accommodate it or scans too infrequently to recoup the investment in the technology.