title: Severity assessment of lower respiratory tract infection in Malawi: derivation of a novel index (SWAT-Bp) which outperforms CRB-65.
abstract: OBJECTIVE
  To assess the validity of CRB-65 (Confusion, Respiratory rate >30 breaths/min, BP<90/60 mmHg, age >65 years) as a pneumonia severity index in a Malawian hospital population, and determine whether an alternative score has greater accuracy in this setting.
  
  
  METHODS
  Forty three variables were prospectively recorded during the first 48 hours of admission in all patients admitted to Queen Elizabeth Central Hospital, Malawi, for management of lower respiratory tract infection over a two month period (N = 240). Calculation of sensitivity and specificity for CRB-65 in predicting mortality was followed by multivariate modeling to create a score with superior performance in this population.
  
  
  RESULTS
  Median age 37, HIV prevalence 79.9%, overall mortality 18.3%. CRB-65 predicted mortality poorly, indicated by the area under the ROC curve of 0.649. Independent predictors of death were: Male sex, "S" (AOR 2.6); Wasting, "W" (AOR 6.6); non-ambulatory, "A" (AOR 2.5); Temp >38°C or <35°C, "T" (AOR 3.2); BP<100/60, "Bp" (AOR 3.7). Combining these factors to form a severity index (SWAT-Bp) predicted mortality with high sensitivity and specificity (AUC: 0.867). Mortality for scores 0-5 was 0%, 3.3%, 7.4%, 29.2%, 61.5% and 87.5% respectively. A score ≥3 was 84% sensitive and 77% specific for mortality prediction, with a negative predictive value of 95.8%.
  
  
  CONCLUSIONS
  CRB-65 performs poorly in this population. The SWAT-Bp score can accurately stratify patients; ≤2 indicates non-severe infection (mortality 4.4%) and ≥3 severe illness (mortality 45%).
authors: Birmingham College of Medicine, Birmingham University, Birmingham, United Kingdom.
authors: Edmund
authors: E
authors: Birkhamshaw
authors: Catriona J
authors: CJ
authors: Waitt
authors: Michael
authors: M
authors: Innes
authors: Peter I
authors: PI
authors: Waitt
mesh_terms: D000368:Aged; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008295:Malawi / Q000453:epidemiology; D008297:Male; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D012372:ROC Curve; D012141:Respiratory Tract Infections / Q000401:mortality / Q000473:pathology*; D012720:Severity of Illness Index