title: Negative predictive value of excluding an embedded snake foreign body by ultrasonography.
abstract: OBJECTIVE
  Numerous reputable sources for healthcare providers advocate routine imaging to rule out an embedded tooth or fang after a snake bite. The objective of this study was to determine whether these foreign bodies can be reliably excluded by bedside ultrasonography.
  
  
  METHODS
  All emergency medicine (EM) residents and faculty at a single institution were invited to participate. Two sets of 5 ultrasound gel phantoms were prepared using a method previously validated to have the same density as human tissue. In the first set of 5 phantoms, 1 snake fang was embedded to simulate a retained foreign body. Similarly, in the second set of 5 phantoms, 1 snake tooth was also embedded. Participants were asked to identify the presence or absence of a foreign body in each phantom using bedside ultrasonography. Year of training and confidence in excluding a snake foreign body were also recorded.
  
  
  RESULTS
  Each participant (n=27) performed ultrasound imaging on 10 phantoms for a total of 270 samples. Range of experience included postgraduate year 1 (25.9%), postgraduate year 2 (29.6%), postgraduate year 3 (33.3%), and graduates of EM residency (11.1%). The sensitivity and negative predictive value for ruling out an embedded fang was 92.6% and 98.1%, respectively. The sensitivity and negative predictive value for ruling out an embedded tooth was 77.8% and 93.7%, respectively. Among all the phantoms, there was a sensitivity of 85.2% and a negative predictive value of 96%.
  
  
  CONCLUSIONS
  Bedside ultrasonography performed by an EM physician is a feasible option to rule out embedded foreign bodies after a snake bite if imaging is warranted.
authors.affiliation: Division of Medical Toxicology, Department of Emergency Medicine (Drs Rushton, Vakkalanka, and Charlton), and the Department of Emergency Medicine (Dr Moak), University of Virginia School of Medicine, Charlottesville, VA. Electronic address: wrushton@gmail.com.
authors.forename: William F
authors.initials: WF
authors.lastname: Rushton
authors.affiliation: Division of Medical Toxicology, Department of Emergency Medicine (Drs Rushton, Vakkalanka, and Charlton), and the Department of Emergency Medicine (Dr Moak), University of Virginia School of Medicine, Charlottesville, VA.
authors.forename: J Priyanka
authors.initials: JP
authors.lastname: Vakkalanka
authors.affiliation: Division of Medical Toxicology, Department of Emergency Medicine (Drs Rushton, Vakkalanka, and Charlton), and the Department of Emergency Medicine (Dr Moak), University of Virginia School of Medicine, Charlottesville, VA.
authors.forename: James H
authors.initials: JH
authors.lastname: Moak
authors.affiliation: Division of Medical Toxicology, Department of Emergency Medicine (Drs Rushton, Vakkalanka, and Charlton), and the Department of Emergency Medicine (Dr Moak), University of Virginia School of Medicine, Charlottesville, VA.
authors.forename: Nathan P
authors.initials: NP
authors.lastname: Charlton
mesh_terms: D000818:Animals; D004632:Emergency Medical Services; D005547:Foreign Bodies / Q000000981:diagnostic imaging*; D006801:Humans; D008953:Models, Anatomic; D015588:Observer Variation; D011237:Predictive Value of Tests; D012909:Snake Bites / Q000000981:diagnostic imaging*; D012911:Snakes; D014070:Tooth; D014463:Ultrasonography
keywords: emergency medicine; foreign body; pit vipers; snake; ultrasound