Bedside Ultrasound: Sorting Shadows
- In a prospective, randomized trial of patients presenting to an ER with respiratory symptoms, standard diagnostic tests supplemented with point-of-care ultrasonography compared with a standard diagnostic strategy alone were associated with a higher rate of correct presumptive diagnoses.
- Despite the increased percentage of patients who were given a correct presumptive diagnosis and appropriate treatment, no difference was noted in patient outcomes such as length of hospital stay and number of readmissions.
Rory Spiegel, MD, is the chief resident in emergency medicine at Newark Beth Israel Medical Center in New Jersey. In his free time he enjoys riding in TARDISes, defending the Wall, and “chasing the wind.” He is a self-described nerd who blogs regularly on nihilism and the art of doing nothing at EMnerd.com, where a version of this article originally appeared.
In this post, Spiegel examines the use of point-of-care ultrasound in relation to a randomized clinical trial recently published in The Lancet Respiratory Medicine.
Truth: It’s Not Always Based in Concrete Reality
In medicine, we frequently propagate half-truths and unsubstantiated certainties. Thus, truth is a relative experience, dependent primarily upon how we choose to define it, rather than any concrete state of reality.
Increasingly, we have favored a technological definition of truth over that of the clinical perspective. As such, we are driven to act in disease states that may be best ignored. Where we draw the line of clinical relevance and subclinical disease seems to depend upon our own comfort with uncertainty.
Given this current culture, it is not surprising that bedside ultrasound has become a popular tool to evaluate the majority of ailments that show up in the emergency department.
With our expanding technical skills, so too has our comfort expanded in using this modality to make clinical decisions. At this point, such a level of technical proficiency has been achieved that we have outpaced the literature base to guide these decisions.
Until recently, the majority of the literature addressing bedside ultrasound has been limited by its use of surrogate endpoints and disease oriented definitions of success. Thus, we stand at a crossroads in emergency medicine.
This is not intended to discredit bedside ultrasound as a modality, but rather a commentary on its user, and our inability to separate clinically relevant reality from the pixelated truth we see on our monitors. And to ask the question, how exactly should we determine our sonographic definition of truth?
Bedside Ultrasound Clinical Trial
A recent article published in The Lancet Respiratory Medicine by Laursen et al., is the first randomized, controlled trial that measures the efficacy of bedside ultrasound using a hard clinical outcome. Until the publication of this article, the efficacy of ultrasound was evaluated through studies addressing its diagnostic accuracy through comparisons with traditional diagnostics.
In many cases ultrasound proved comparable, or even superior to traditional diagnostic modality. These types of studies helped us define the potential utility of bedside ultrasound, but we have outgrown these humble beginnings.
What is now required are trials examining the patient-centered effects of the incorporation of bedside ultrasound into our practice.
The findings of the trial by Laursen et al., were covered in more detail in my previous post found on EM Literature of Note and examined in an even more expert fashion by Simon Carly on The St. Emlyn’s blog. I have included an excerpt from my post as a summation of these findings:
“Authors randomized patients presenting to the emergency department with signs or symptoms concerning a respiratory etiology to either a standard workup as determined by the treating physician, or the addition of POCUS [point-of-care ultrasound] performed by a single experienced operator.
“The ultrasound protocol consisted of sonographic examination of the heart, lungs, and lower extremity deep veins to identify possible causes of patients’ symptoms. The authors’ primary outcome was the percentage of patients with a correct presumptive diagnosis 4 hours after presentation to the emergency department as determined by two physicians blinded to emergency department POCUS findings, but with access to the records of the entire hospital stay.
“Using the POCUS protocol, the authors found stunning success in their primary endpoint. Specifically, the rate of correct diagnoses made at 4-hours in the POCUS group was 88% compared with 63.7% in the standard workup group. Furthermore, 78% of the patients in the POCUS group received “appropriate” treatment in the emergency department compared with 56.7% in the standard workup group.”
Though promising, these benefits did not translate into improvements in true patient-oriented benefits. And, although not statistically significant, the observed in-hospital (8.2% versus 5.1%) and 30-day mortality trended towards harm in the POCUS arm (12% versus 7%).
Also, there weren’t any meaningful differences in length of stay or hospital-free days between the POCUS group and the control group. Even more concerning, were the significant increases in downstream testing that occurred in patients randomized to the POCUS group:
- Chest CTs, 8.2% versus 1.9%
- Echocardiograms, 10.1% versus 3.8%
- Diagnostic thoracentesis, 5.7% versus 0%
It is important to note the pathologies found in the POCUS group were not false positives, as confirmed by additional diagnostic tests. As such, this is not a question of technical competency, but rather a question of clinical relevancy.
The significant increase in diagnostic proficiency found in the POCUS group did not result in improved patient-oriented outcomes. In fact, there were significant trends towards harm in both hospital and 30-day mortality.
This, of course, may be statistical whimsy.
Future trials might show this to be nothing more than the random noise generated by a small sample size, but these findings are concerning for a certain degree of overdiagnosis.
Updating Clinical Practice
The trial by Laursen et al., is not a solitary signal standing out from a crowd of contrary data. There have been signs throughout ultrasound literature demonstrating the potential for overdiagnosis, as I discuss in a sidebar here.
How do we move forward? Ultrasound has been traditionally examined as a diagnostic test, meaning its utility is routinely compared with a gold standard. Ultrasound studies of pneumonias, pneumothoraxes, appendicitis, or peritoneal injury are commonly evaluated against CT.
It is an exciting time in the world of point-of-care ultrasound. There are great minds with extraordinary vision pushing this field forward every day. It is a privilege to experience this progression. But as technology advances and the quality of our point-of-care machinery improves, overdiagnosis will become an evermore imperative concern.
We need to utilize patient relevant outcomes when evaluating the use of bedside ultrasound in order to assess its true value as a diagnostic tool.
If we choose to stick our heads in the sand, holding fast to unquestionable certainty found in our periodic interpretation of shadows, we will surely redefine medical truth for the worst. Like CT pulmonary angiogram once changed the diagnosis of pulmonary embolism from a clinically relevant dangerous disease to a primarily irrelevant disease-oriented definition, point-of-care ultrasound will identify a large quantity of subclinical disease of questionable clinical bearing.
Conversely, if we choose to continue to question the proper application of point-of-care ultrasound and focus not only on our procedural expertise but on our medical stewardship we will progress the field of bedside ultrasound and improve patient care.
If we are to claim clinical expertise, our knowledge must extend beyond the technical proficiencies and integrate the wisdom needed to interpret these shadows.
For more EMnerd:
Laursen receives royalties from UltraSound Airway Breathing Circulation Dolor (USabcd) as an author of e-learning material and has been paid as the director or instructor for courses in ultrasound organised by USabcd. Madsen received a lecture fee from InterMune in 2014, travel expenses and congress and symposium fees covered by Norphama in 2013, travel expenses and symposium fees covered by Novartis in 2012, travel expenses and symposium fees covered by Nycomed, Chiesi Pharmaceuticals, Boehringer Ingelheim, and Pfizer in 2011. Davidsen declares sponsored participation at European Respiratory Society Congress in 2013 by Boehringer Ingelheim, two Novartis-sponsored symposiums in 2011 and 2012, and a Norpharma-sponsored symposium in 2013. The other authors declare no competing interests.
Primary source: The Lancet Respiratory Medicine
Source reference: Laursen CB, et al “Point-of-care ultrasonography in patients admitted with respiratory symptoms: a single-blind, randomised controlled trial” Lancet Respir Med2014; DOI: 10.1016/S2213-2600(14)70135-3.