title: Disaster Metrics: Evaluation of de Boer's Disaster Severity Scale (DSS) Applied to Earthquakes.
abstract: BACKGROUND
  Quantitative measurement of the medical severity following multiple-casualty events (MCEs) is an important goal in disaster medicine. In 1990, de Boer proposed a 13-point, 7-parameter scale called the Disaster Severity Scale (DSS). Parameters include cause, duration, radius, number of casualties, nature of injuries, rescue time, and effect on surrounding community. Hypothesis This study aimed to examine the reliability and dimensionality (number of salient themes) of de Boer's DSS scale through its application to 144 discrete earthquake events.
  
  
  METHODS
  A search for earthquake events was conducted via National Oceanic and Atmospheric Administration (NOAA) and US Geological Survey (USGS) databases. Two experts in the field of disaster medicine independently reviewed and assigned scores for parameters that had no data readily available (nature of injuries, rescue time, and effect on surrounding community), and differences were reconciled via consensus. Principle Component Analysis was performed using SPSS Statistics for Windows Version 22.0 (IBM Corp; Armonk, New York USA) to evaluate the reliability and dimensionality of the DSS.
  
  
  RESULTS
  A total of 144 individual earthquakes from 2003 through 2013 were identified and scored. Of 13 points possible, the mean score was 6.04, the mode = 5, minimum = 4, maximum = 11, and standard deviation = 2.23. Three parameters in the DSS had zero variance (ie, the parameter received the same score in all 144 earthquakes). Because of the zero contribution to variance, these three parameters (cause, duration, and radius) were removed to run the statistical analysis. Cronbach's alpha score, a coefficient of internal consistency, for the remaining four parameters was found to be robust at 0.89. Principle Component Analysis showed uni-dimensional characteristics with only one component having an eigenvalue greater than one at 3.17. The 4-parameter DSS, however, suffered from restriction of scoring range on both parameter and scale levels.
  
  
  CONCLUSIONS
  Jan de Boer's DSS in its 7-parameter format fails to hold statistically in a dataset of 144 earthquakes subjected to analysis. A modified 4-parameter scale was found to quantitatively assess medical severity more directly, but remains flawed due to range restriction on both individual parameter and scale levels. Further research is needed in the field of disaster metrics to develop a scale that is reliable in its complete set of parameters, capable of better fine discrimination, and uni-dimensional in measurement of the medical severity of MCEs.
authors.affiliation: 1Department of Emergency Medicine,Johns Hopkins School of Medicine,Baltimore,MarylandUSA.
authors.forename: Jamil D
authors.initials: JD
authors.lastname: Bayram
authors.affiliation: 2Orange Coast Memorial Medical Center,Department of Emergency Medicine,Orange County,CaliforniaUSA.
authors.forename: Shawki
authors.initials: S
authors.lastname: Zuabi
authors.affiliation: 1Department of Emergency Medicine,Johns Hopkins School of Medicine,Baltimore,MarylandUSA.
authors.forename: Caitlin M
authors.initials: CM
authors.lastname: McCord
authors.affiliation: 3Hampshire College,Amherst,MassachusettsUSA.
authors.forename: Raphael A G
authors.initials: RA
authors.lastname: Sherak
authors.affiliation: 1Department of Emergency Medicine,Johns Hopkins School of Medicine,Baltimore,MarylandUSA.
authors.forename: Edberdt B
authors.initials: EB
authors.lastname: Hsu
authors.affiliation: 1Department of Emergency Medicine,Johns Hopkins School of Medicine,Baltimore,MarylandUSA.
authors.forename: Gabor D
authors.initials: GD
authors.lastname: Kelen
mesh_terms: D004189:Disaster Planning; D004190:Disasters / Q000145:classification*; D055866:Earthquakes; D006801:Humans; D054527:Mass Casualty Incidents; D025341:Principal Component Analysis; D011446:Prospective Studies; D015203:Reproducibility of Results; D015599:Trauma Severity Indices
keywords: DSS Disaster Severity Scale; MCE multiple-casualty event; MMI Modified Mercalli Intensity; NOAA National Oceanic and Atmospheric Administration; USGS US Geological Survey; multiple-casualty events