title: Anion and osmolal gaps in the diagnosis of methanol poisoning: clinical study in 28 patients.
abstract: OBJECTIVE
  To evaluate anion and osmolal gaps as diagnostic tools in methanol poisoning.
  
  
  METHODS
  Clinical observational study.
  
  
  METHODS
  In a recent methanol outbreak, the initial triage and treatment decisions in 28 patients were based mainly upon the values of the osmolal and anion gaps on admission. Methanol and formate levels were later compared to these gaps by linear regression analysis.
  
  
  RESULTS
  The correlation between the osmolal gaps and serum methanol concentrations on admission was linear (y = 1.03x+12.71, R2 = 0.94). The anion gaps correlated well with the serum formate concentrations (y = 1.12x+13.82, R2 = 0.86). Both gaps were elevated in 24 of the 28 subjects upon admission. Three patients had an osmolal gap within the reference area (because of low serum methanol), but elevated anion gap because of formate accumulation. One patient with probable concomitant ethanol ingestion had a high osmolal gap and a normal anion gap.
  
  
  CONCLUSIONS
  Osmolal and anion gaps are useful in the diagnosis and triage of methanol-exposed subjects. Confounders are low serum methanol and concomitant ethanol ingestion.
authors.affiliation: Department of Acute Medicine, Ullevaal University Hospital, 0407 Oslo, Norway. knuterik.hovda@ulleval.no
authors.forename: Knut Erik
authors.initials: KE
authors.lastname: Hovda
authors.forename: Odd Helge
authors.initials: OH
authors.lastname: Hunderi
authors.forename: Nina
authors.initials: N
authors.lastname: Rudberg
authors.forename: Sten
authors.initials: S
authors.lastname: Froyshov
authors.forename: Dag
authors.initials: D
authors.lastname: Jacobsen
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000175:diagnosis; D002849:Chromatography, Gas; D005561:Formates / Q000097:blood; D006801:Humans; D016014:Linear Models; D000432:Methanol / Q000097:blood / Q000506:poisoning*; D019370:Observation; D011041:Poisoning / Q000097:blood* / Q000175:diagnosis; D012997:Solvents / Q000032:analysis / Q000506:poisoning
chemical_list: D005561:Formates; D012997:Solvents; C030544:formic acid; D000432:Methanol