title: Validity of British Thoracic Society guidance (the CRB-65 rule) for predicting the severity of pneumonia in general practice: systematic review and meta-analysis.
abstract: BACKGROUND
  The CRB-65 score is a clinical prediction rule that grades the severity of community-acquired pneumonia in terms of 30-day mortality.
  
  
  OBJECTIVE
  The study sought to validate CRB-65 and assess its clinical value in community and hospital settings.
  
  
  METHODS
  Systematic review and meta-analysis of validation studies of CRB-65.
  
  
  METHODS
  Medline (1966 to June 2009), Embase (1988 to November 2008), British Nursing Index (BNI) and PsychINFO were searched, using a diagnostic accuracy search filter combined with subject-specific terms. The derived (index) rule was used as a predictive model and applied to all validation studies. Comparison was made between the observed and predicted number of deaths stratified by risk group (low, intermediate, and high) and setting of care (community or hospital). Pooled results are presented as risk ratios (RRs) in terms of over-prediction (RR>1) or under-prediction (RR<1) of 30-day mortality.
  
  
  RESULTS
  Fourteen validation studies totalling 397 875 patients are included. CRB-65 performs well in hospitalised patients, particularly in those classified as intermediate (RR 0.91, 95% confidence interval [CI] = 0.71 to 1.17) or high risk (RR 1.01, 95% CI = 0.87 to 1.16). In community settings, CRB-65 over-predicts the probability of 30-day mortality across all strata of predicted risk, low (RR 9.41, 95% CI = 1.75 to 50.66), intermediate (RR 4.84, 95% CI = 2.61 to 8.69), and high (RR 1.58, 95% CI = 0.59 to 4.19).
  
  
  CONCLUSIONS
  CRB-65 performs well in stratifying severity of pneumonia and resultant 30-day mortality in hospital settings. In community settings, CRB-65 appears to over-predict the probability of 30-day mortality across all strata of predicted risk. Caution is needed when applying CRB-65 to patients in general practice.
authors.affiliation: HRB Centre for Primary Care Research, Department of General Practice, Royal College of Surgeons in Ireland Medical School, Dublin, Ireland.
authors.forename: Maggie
authors.initials: M
authors.lastname: McNally
authors.forename: James
authors.initials: J
authors.lastname: Curtain
authors.forename: Kirsty K
authors.initials: KK
authors.lastname: O'Brien
authors.forename: Borislav D
authors.initials: BD
authors.lastname: Dimitrov
authors.forename: Tom
authors.initials: T
authors.lastname: Fahey
mesh_terms: D005194:Family Practice; D006801:Humans; D011014:Pneumonia / Q000175:diagnosis* / Q000401:mortality; D011379:Prognosis; D018570:Risk Assessment; D012720:Severity of Illness Index; D006113:United Kingdom; D054928:Validation Studies as Topic