title: Methanol and ethylene glycol acute poisonings - predictors of mortality.
abstract: BACKGROUND
  Methanol and ethylene glycol cause significant mortality post-ingestion. Predicting prognosis based on the biomarkers osmolal gap, anion gap and pH is beneficial.
  
  
  OBJECTIVE
  To evaluate the relationship between biomarkers, measured post-methanol and ethylene glycol exposure, and clinical outcomes.
  
  
  METHODS
  A review of the literature identified cases where methanol or ethylene glycol had been ingested and clinical outcomes were recorded. Biomarkers were extracted including osmolal gap, anion gap and pH, with clinical outcomes categorised as recovered, recovered with adverse sequelae and death. Biomarkers were analysed using the Mann-Whitney test for two samples; sensitivity and specificity were evaluated using receiver operating characteristic (ROC) curves.
  
  
  RESULTS
  In total, 119 cases of methanol and 88 of ethylene glycol poisoning were identified; 21 methanol and 19 ethylene glycol patients died. For methanol ingestion the mean values, for survival compared to death, were 48 (range: 6-138) and 90 (range: 49-159) mOsm/kg water for osmolal gap (p=0.0052), 31 (range: 11-50) and 41 (range: 30-53) mmol/L for anion gap (p=0.0065) and 7.21 (range: 6.60-7.50) and 6.70 (range: 6.34-7.22) for arterial pH (p<0.0001). The area under the ROC curve was highest for arterial pH, 0.94 (95% CI: 0.89-0.99). For ethylene glycol, these were 49 (range: 0-189) and 79 (range: 25-184) mOsm/kg water for osmolal gap (p=0.050), 28 (range: 6-48) and 38 (range: 20-66) mmol/L for anion gap (p=0.0037) and 7.08 (range: 6.46-7.39) and 6.98 (range: 6.50-7.16) for pH (p=0.072), for survival compared to death. The area under the ROC curve was highest for anion gap, 0.73 (95% CI: 0.60-0.87).
  
  
  CONCLUSIONS
  Post-methanol ingestion a large osmolal gap, anion gap and low pH (<7.22) were associated with increased mortality; and pH has the highest predictive value. Post-ethylene glycol ingestion, both osmolal gap and anion gap were associated with increased mortality.
authors.affiliation: School of Pharmacy, University of Otago, Dunedin, New Zealand. carolyn.coulter@otago.ac.nz
authors.forename: Carolyn V
authors.initials: CV
authors.lastname: Coulter
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Farquhar
authors.forename: Claire M
authors.initials: CM
authors.lastname: McSherry
authors.forename: Geoffrey K
authors.initials: GK
authors.lastname: Isbister
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Duffull
mesh_terms: D000136:Acid-Base Equilibrium; D015415:Biomarkers / Q000378:metabolism*; D019855:Ethylene Glycol / Q000506:poisoning*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000432:Methanol / Q000506:poisoning*; D009994:Osmolar Concentration; D011041:Poisoning / Q000097:blood / Q000401:mortality; D011379:Prognosis; D012372:ROC Curve; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
chemical_list: D015415:Biomarkers; D019855:Ethylene Glycol; D000432:Methanol