Test Characteristics of Point of Care Ultrasound for the Diagnosis of Retinal Detachment in the Emergency Department

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.

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