Author: UCSD Ultrasound

What is the feasibility and diagnostic accuracy of PoCUS for the management of acute dyspnea in the ED?

• Design:

Prospective, blinded, observational study

• Population:

This study was conducted at Careggi University Hospital, a university-affiliated teaching hospital.

• Inclusion Criteria:

Patients over the age of 18 with acute dyspnea of any degree. 

• Exclusion Criteria:

Patients with dyspnea of traumatic origin, and those that were discharged from the emergency department after evaluation. 

• Intervention:

All patients were primarily assessed by 2 separate emergency physicians with vital signs, history, physical exam, and EKG.

One physician performed a Lung, Cardiac, and IVC PoCUS.

One physician performed a standard workup using any combination of Chest X-Ray, Chest CT, Echocardiogram, labs, or Arterial Blood Gas.

Both physicians were asked to make up to 2 diagnoses based on their results.

Possible diagnoses: Heart Failure, Acute Coronary Syndrome, Pneumonia, Pleural Effusion, Pericardial Effusion, COPD/asthma, Pulmonary Embolism, Pneumothorax, ARDS/ALI, Other.

• Outcomes

Primary: 

Accuracy of diagnosis:

Follow-up chart review determined the reference diagnosis. Results were compared to the diagnosis obtained from the ultrasound group and the standard workup group.

Secondary: 

Time to final diagnosis for both groups was recorded.

Time for Ultrasound completion was recorded.

3,487 total patients → 2,683 included in study

Average time to complete US: 7±2 min

Average time to Diagnosis:

Ultrasound: 24 ± 10 minutes

ED: 186 ± 72 minutes

Variable	Sensitivity - Ultrasound	Sensitivity - Standard
Heart Failure	88 (85.1-90.6)	77.3 (73.7 – 80.6)
COPD/asthma	86.6 (84.2-89.2)	92.2 (90.1-94)
Pulmonary Embolism	40 (30.1-50.6)	90.5 (82.8-95.6)

• Point-of-care ultrasound had an increased sensitivity in detecting heart failure compared to standard workup.
• Point-of-care ultrasound had a decreased sensitivity in diagnosing COPD/asthma and pulmonary embolism compared to standard workup.

There were no differences in the sensitivity or specificity of ultrasound vs. standard workup in all other diagnoses.

Strengths

Adequate sample size obtained for most diagnoses.

Gold standard diagnosis was reviewed by two separate emergency medicine physicians.

Limitations

Ultrasound sonographers focused only on those patients with dyspnea, while the treating physicians were responsible for other patients in the ED.

This likely increased the time to diagnosis for emergency physicians in the standard workup group.

Patients discharged from the hospital were not included in study.

Average age of patient population was 71, but patients 18 and over were accepted.

ARDS patient studies were underpowered.

“Integrated ultrasound methods could replace the current first diagnostic approach to patients presenting with dyspnea, allowing a drastic reduction in costs and diagnostic times.”

Point-of-Care Ultrasound in patients with dyspnea provides us with quick information to begin treatment before other laboratory and radiological tests become available. While this study showed that ultrasound was superior to the standard workup in detecting heart failure, it was slightly inferior to the standard workup in detecting COPD/asthma, and significantly inferior to standard workup in detecting pulmonary embolism. The authors speculated that with the inclusion of a DVT ultrasound study would improve the sensitivity for detecting PEs greatly.  

There have been other studies demonstrating increased sensitivity using ultrasound in patients to diagnose pneumonia and pleural effusions compared to chest x-ray. This study contributed to our knowledge of the accuracy of ultrasound in undifferentiated dyspnea by demonstrating its accuracy in these other important diagnoses. The study shows that PoCUS can guide and the emergency physician’s workup, help risk-stratify, can help us to begin treatment quickly, and improveflow and efficiency in the ED. 

This post was written by Marissa Wolfe, MS4 at Stony Brook University. Review and further commentary was provided by Amir Aminlari, MD, Ultrasound Faculty at UCSD.

1. Mulrow CD, Lucey CR, Farnett LE. Discriminating causes of dyspnea through clinical examination. J Gen Intern Med. 1993;8(7):383-392. 
2. Schmitt BP, Kushner MS, Wiener SL. The diagnostic usefulness of the history of the patient with dyspnea. J Gen Intern Med. 1986;1(6):386-393. 
3. Nielsen LS, Svanegaard J, Wiggers P, Egeblad H. The yield of a diagnostic hospital dyspnoea clinic for the primary health care section. J Intern Med. 2001;250(5):422-428. 
4. Lichtenstein D, Mezière G. Relevance of lung ultrasound in the diagnosis of acute respiratory failure: the BLUE protocol. Chest. 2008;134(1):117-125. 
5. Reissig A, Copetti R, Mathis G, et al. Lung ultrasound in the diagnosis and follow-up of community-acquired pneumonia: a prospective, multicenter, diagnostic accuracy study. Chest. 2012;142(4): 965-972. 
6. Zanobetti M, Poggioni C, Pini R. Can chest ultrasonography replace standard chest radiography for evaluation of acute dyspnea in the ED? Chest. 2011;139(5): 1140-1147. 
7. Nazerian P, Volpicelli G, Vanni S, et al. Accuracy of lung ultrasound for the diagnosis of consolidations when compared to chest computed tomography. Am J Emerg Med. 2015;33(5):620-625. 

What are the test characteristics (sensitivity and specificity) of POCUS for the diagnosis of RD in patients presenting with chief complaint of flashes or floaters, when performed by a group of emergency physicians with varying degrees of ultrasound experience?

• Design
  • Prospective study using a convenience sample of patients presenting to the ED with a chief complaint of flashes or floaters in visual fields
• Population
  • Conducted at Vancouver General Hospital, an urban academic tertiary care center
• Inclusion Criteria
  • Patients presenting with chief complaint of acute (7 days or less) onset flashes or floaters in one or both eyes between March 2015 and September 2016
• Exclusion Criteria
  • Age younger than 19 years, known diagnosis of RD, exam compromised due to advanced cataract in the affected eye, ophthalmologic surgery on affected eye within prior two weeks
• Intervention
  • EP performed ocular POCUS with high-frequency linear transducer
  • Scan performed in both transverse and longitudinal plane with dynamic assessment of posterior chamber (patient looking left/right and up/down)
  • Positive or negative interpretation for RD was recorded
  • Reference Standard
    • Patients were referred to an ophthalmology resident who performed non-blinded assessment including a complete dilated retinal exam
    • Patients were then seen by a retina specialist blinded to the ED POCUS within 1 week, or for patients with a retinal tear or RD diagnosis, within 1 day
  • Standardized training session for emergency providers
    • EM attendings (20), fellows (2), and residents (8) of varying ultrasound experience received a 1 hour lecture on the use of POCUS to detect RD
    • All participating EPs performed one practice scan on a healthy volunteers
• Outcomes
  • Primary outcome: Accuracy of the EP diagnosis with respect to the reference standard, the retina specialist diagnosis
  • Test characteristics: sensitivity, specificity, diagnostic accuracy, LR+, and LR- 

Flow of Patients Through Study

Primary analysis

• • Sensitivity: 75% (95% CI 48-93%)
  • Specificity: 94% (95% CI 87-98%)
  • Diagnostic accuracy: 91% (95% CI 85-96%)
  • LR-positive: 12.4 (95% CI 5.4-28.3)
  • LR-negative: 0.27 (95% CI 0.11-0.62)

Secondary analyses

• • Test characteristics by level of training
    • Residents and fellows: 100% sensitivity, 95% specificity
    • Attending physicians: 71% sensitivity, 94% specificity
  • Test characteristics by number of patients enrolled by EP
    • 1-2 patients enrolled: 80% sensitivity, 71% specificity
    • 3 or more patients enrolled: 73% sensitivity, 98% specificity

• • Insufficiently powered for the secondary analyses
  • Single program study limits generalizability
  • Prior ultrasound experience was not explicitly assessed
  • RD is not always classically presenting, starting with a population defined by classic symptoms may influence observed test characteristics

“In a heterogeneous group of EPs with varying ultrasound experience, POCUS demonstrates high specificity but only intermediate sensitivity for the detection of RD. A negative POCUS scan in the ED performed by a heterogeneous group of providers after a one-hour POCUS didactic is not sufficiently sensitive to rule out RD in a patient with new onset flashes or floaters.”

This study demonstrates that emergency physicians of varying training levels and ultrasound experience can successfully employ POCUS in the diagnosis of RD after only a short training session. By incorporating POCUS into the workup of patients presenting with ocular complaints characteristic of RD, true pathology can be identified with high specificity. Appropriate care can then be mobilized expeditiously in these scan-positive patients in order to prevent the permanent vision loss associated with this condition.

Indeed, a 74% sensitivity is too low for POCUS to reliably be utilized by a heterogeneous population of EPs as a tool to rule-out RD, especially given the consequences of a missed diagnosis. It would be reasonable practice, therefore, as the authors suggest, for all patients with new onset flashes and/or floaters to continue be referred for further ophthalmologic evaluation to definitively rule-out RD and other conditions at-risk for progression to RD. It should also be noted, however, that a trend towards increased specificity was observed amongst physicians who enrolled more patients in this study. Taken in context with test characteristics reported in prior literature, these findings may suggest that specificity can be improved upon with experience, and in the hands of a trained sonographer, POCUS may also be used as a tool to reliably rule-out RD.

This post was written by Oretunlewa Soyinka, MS4 at UCSD. Review and further commentary was provided by Cameron Smyres, MD, Ultrasound Fellow at UCSD.

1 .  Hikichi T, Hirokawa H, Kado M, et al. Comparison of the prevalence of posterior vitreous
detachment in whites and Japanese. Ophthalmic Surg 1995; 26:39-43.

2.  Hollands H, Johnson D, Brox AC, et al. Acute-onset floaters and flashes: is this patient at
risk for retinal detachment? JAMA 2009; 302:2243-9

3.  Alotaibi AG, Osman EA, Allam KH, et al. One month outcome of ocular related
emergencies in a tertiary hospital in Central Saudi Arabia. Saudi Med J 2011; 32:1256-60.

4.  Mitry D, Charteris DG, Fleck BW, et al. The epidemiology of rhegmatogenous retinal
detachment: geographical variation and clinical associations. Br J Ophthalmol 2010;
94:678-84.