1. References: Available upon request
Test Characteristics of Point of Care Ultrasound for the Diagnosis of Retinal Detachment in the Emergency Department
Mario Francispragasam1, Gavin Docherty2, Byron Silver3, Ross Prager3 Donna Lee1,4, David Maberley2, Daniel Kim1,4
Study Objectives
Methods and Materials
Results
Discussion
To date, this is the largest prospective study assessing the use of POCUS for the diagnosis of RD in the ED. While previous studies have suggested that EPs can use ocular ultrasound to diagnose RD with a high degree of sensitivity and specificity, we were unable to replicate the high sensitivity demonstrated in the published emergency medicine literature. Our high specificity is consistent with previous studies.
Review of the false positive and false negative results demonstrates that the most commonly confused alternate diagnoses were posterior vitreous detachment and vitreous hemorrhage.
Limitations: We would like to acknowledge several limitations in our study. Despite a higher case number than previous studies the number of RD’s was limited. This constrains the ability to analyze trends in POCUS diagnosis of RD and if there are specific variables leading to false positive and negative diagnosis. Although we assessed the level of training of the EP’s performing POCUS our study was not structured or powered sufficiently to compare level of training in the use of POCUS for diagnosis of RD. Furthermore, in the case of an incomplete posterior vitreous detachment it is possible that a retinal tear or RD could develop between the time of initial assessment and the retina specialist referral. However, this is extremely unlikely. Finally, POCUS protocol did not mandate that the gain be increased when evaluating for RD.
Our primary objective was to assess the test characteristics of Point of Care Ultrasound (POCUS) performed by a large heterogeneous group of emergency physicians (EPs) for the diagnosis of (RD).
Methods of Measurement: Physician participation in this study was open to all emergency medicine staff, fellows, and residents, regardless of prior ultrasound experience. All participating EPs received a one-hour didactic lecture on using POCUS to detect retinal detachment. EPs were expected to demonstrate adequate performance of one practice scan prior to enrolling patients.
Participants were initially assessed in the ED by an emergency physician (EP) who then performed an ocular POCUS using Sonosite Edge (Bothell, WA) with high frequency linear L25x transducer (6-13MHz). Scanning was performed on the highest frequency setting and used a dynamic assessment protocol. Patients were then referred to the on-call ophthalmology resident who facilitated referral to a retinal specialist. A retina specialist saw all cases of RD and retinal tears within 24 hours.
A total of 128 patients were enrolled, of whom 2 met exclusion criteria (Figure 1). Reference standard was available in 115 patients for final analysis. Of these 115 patients, the median age was 60 years (IQR years), and 64% were female.
Of the 115 study patients, the retina specialist diagnosed RD in 16 (14%) cases. In the same population, EPs diagnosed RD on POCUS in 18 (16%) cases.
Table 1 shows the contingency table used to calculate diagnostic indexes. The sensitivity and specificity of POCUS by EPs for RD was 75% (95% CI 48-93%) and 94% (95% CI 87-98%), respectively. Diagnostic accuracy was 91% (95% CI 85-96%). The positive likelihood ratio was 12.4 (95% CI ), and the negative likelihood ratio was 0.27 (95% CI ).
Introduction
The acute onset of flashes and floaters in the eyes is a common presentation to both primary care and emergency physicians and is a leading cause of referral to ophthalmologists. The most common cause of acute onset flashes and floaters is posterior vitreous detachment (PVD). The prevalence of PVD increases with age from about 4% in the 5th decade of life to 87% in individuals over 80 years1. PVD is often a benign process but can result in a retinal tear in approximately 14% of patients2. RD occurs with an incidence of per 10,000 persons per year3-6. Timely diagnosis of PVD followed by complete ophthalmologic exam to rule out a tear or RD is crucial.
Point of care ultrasound (POCUS) has been identified as a useful bedside tool to assess patients for RD, PVD and other retinal pathology7. Recent emergency medicine literature reports sensitivities of % and specificities of % for the test characteristics of POCUS for RD7,9-11. However, these studies are limited by small patient numbers, use of highly trained and experienced sonographers, variability in scanning technique, incomplete blinding and referral bias.
Figure 2.
Graphic representation of the number of scans with results for each EP in the study.
Figure 1. Patient enrollment
Conclusions
We were unable to replicate the high sensitivity of ultrasound for the diagnosis of RD demonstrated in the published emergency medicine literature. 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 is not sufficiently sensitive to rule out RD in a patient with new onset flashes or floaters. These patients still require urgent ophthalmologic assessment. There is a need for larger prospective studies of EP-performed POCUS to determine the amount of training required for EPs to accurately diagnose RD.
Methods and Materials
Study Design: Prospective diagnostic assessment of POCUS for RD performed on a convenience sample. Approved by the UBC Clinical Research Ethics Board. Written and informed consent was obtained.
Setting: Vancouver General Hospital an academic tertiary care hospital with an annual census of 95, 000 emergency department (ED) visits and an affiliated emergency medicine residency program.
Selection: Eligible patients where those who presented to the ED with acute onset of flashers in one or both eyes. Exclusion criteria included age younger than 19, inability or refusal to provide consent, symptom duration greater than 7 days, known diagnosis of RD prior to ED assessment, advanced cataract limiting clinical evaluation or recent ophthalmic surgery in the affected eye.
POCUS
RD Positive
RD Negative
Total
Positive 12 6 18
Negative 4 93 97 16 99
115
Table 1. Diagnostic accuracy of point of care ultrasound for the detection of retinal detachment. CI = Confidence interval. Sensitivity 75% (95% CI 48-93%), specificity 94% (95% CI 87-98%), positive likelihood ratio 12.4 (95% CI ), negative likelihood ratio 0.27 (95% CI ).
Author Affiliations
Department of Emergency Medicine, University of British Columbia, Vancouver, British Columbia, Canada
Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
Faculty of Medicine, MD Undergraduate Program, University of British Columbia, Vancouver, British Columbia, Canada
Department of Emergency Medicine, Vancouver General Hospital, Vancouver, British Columbia, Canada
Contact
Dr. Daniel J. Kim
Department of Emergency Medicine, University of British Columbia
References: Available upon request