Derivation and Validation of the SWAP Score for Very Early Prediction of Neurologic Outcome in Patients With Out-of-Hospital Cardiac Arrest

Ann Emerg Med. 2019 Jun;73(6):578-588. doi: 10.1016/j.annemergmed.2019.01.017. Epub 2019 Feb 26.


Study objective: For patients with out-of-hospital cardiac arrest who receive cardiopulmonary resuscitation in an emergency department (ED), the early evaluation of their neurologic prognosis is essential for emergency physicians. The aim of this study is to establish a simple and useful assessment tool for rapidly estimating the prognosis of patients with out-of-hospital cardiac arrest after their arrival at an ED.

Methods: A total of 852 patients admitted from January 1, 2015, to June 30, 2017, were prospectively registered and enrolled in the derivation cohort. Multivariate logistic regression on this cohort identified 4 independent factors associated with unfavorable outcomes: initial nonshockable rhythm (odds ratio [OR] 3.40; 95% confidence interval [CI] 1.58 to 7.32), no witness of collapse (OR 3.19; 95% CI 1.51 to 6.75), older than 60 years (OR 3.65; 95% CI 1.64 to 8.09), and pH less than or equal to 7.00 (OR 3.27; 95% CI 1.42 to 7.54). The shockable rhythm-witness-age-pH (SWAP) score was developed and 1 point was assigned to each predictor.

Results: For a SWAP score of 4, the specificity was 97.14% (95% CI 91.62% to 100%) for unfavorable outcomes in the derivation cohort. For validation, we retrospectively collected data for 859 patients with out-of-hospital cardiac arrest from January 1, 2012, to December 31, 2014. A SWAP score of 4 was 100% specific (95% CI 99.9% to 100%) for unfavorable outcomes in the validation cohort.

Conclusion: The SWAP score is a simple and useful predictive model that may provide information for the very early estimation of prognosis for patients with out-of-hospital cardiac arrest. Further research is required to integrate ultrasonographic findings and validate the SWAP score's application in other populations.

Publication types

  • Observational Study
  • Research Support, Non-U.S. Gov't
  • Validation Study

MeSH terms

  • Adult
  • Aged
  • Cardiopulmonary Resuscitation*
  • China / epidemiology
  • Emergency Medical Services*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neurodegenerative Diseases / diagnosis*
  • Neurodegenerative Diseases / physiopathology
  • Neurodegenerative Diseases / therapy
  • Neurologic Examination
  • Out-of-Hospital Cardiac Arrest / complications*
  • Out-of-Hospital Cardiac Arrest / physiopathology
  • Out-of-Hospital Cardiac Arrest / therapy
  • Predictive Value of Tests
  • Prospective Studies
  • Registries / statistics & numerical data*