title: Pulmonary embolism rule-out criteria (PERC) in pulmonary embolism--revisited: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To perform a systematic review and meta-analysis including all the current studies to assess the accuracy of pulmonary embolism rule-out criteria (PERC) in ruling out pulmonary embolism (PE).
  
  
  METHODS
  We conducted a comprehensive search of the major databases (Ovid Medline In-Process & Other Non-Indexed Citations, Ovid MEDLINE, Ovid EMBASE, Ovid PsycInfo, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews and Scopus) and references of potentially eligible articles and conference proceedings of major emergency medicine organisations through May 2012. We included all original research studies conducted in emergency departments on diagnostic performance of PERC. Two reviewers independently identified the eligible studies and extracted data. Sensitivity, specificity and likelihood ratios were calculated using contingency tables.
  
  
  RESULTS
  12 studies including 13 cohorts (three retrospective, 10 prospective) were included, comprising of 14 844 patients from six countries. 12 cohorts were urban and one was rural. Pooled (95% CI) sensitivity, specificity, positive and negative likelihood ratio were 0.97 (0.96 to 0.98), 0.22 (0.22 to 0.23), 1.22 (1.16 to 1.29) and 0.17 (0.13 to 0.23), respectively. The pooled (95% CI) diagnostic OR was 7.4 (5.5-9.8). On meta-regression analysis, there was no significant difference between PE prevalence and PERC diagnostic performance (coefficient (SE) of -0.032 (0.022), p=0.173) or on relative diagnostic OR (0.97, 95% CI 0.92 to 1.02). Significant heterogeneity was observed in specificity (I(2)=97.4%) and positive likelihood ratio (I(2)=89.1%).
  
  
  CONCLUSIONS
  Because of the high sensitivity and low negative likelihood ratio, PERC rule can be used confidently in clinically low probability population settings.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. singh.balwinder@mayo.edu
authors.forename: Balwinder
authors.initials: B
authors.lastname: Singh
authors.forename: Shannon K
authors.initials: SK
authors.lastname: Mommer
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Erwin
authors.forename: Soniya S
authors.initials: SS
authors.lastname: Mascarenhas
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Parsaik
mesh_terms: D003661:Decision Support Techniques; D003937:Diagnosis, Differential; D006801:Humans; D016013:Likelihood Functions; D011655:Pulmonary Embolism / Q000175:diagnosis*; D012680:Sensitivity and Specificity