BACKGROUND:Measurement of the osmol gap (OG) is a technique that is used frequently in toxic alcohol poisonings (ethylene glycol (EG) and methanol) as a rapid means to estimate exposure, and can be performed in virtually all hospital laboratories. The value of the OG has not been previously evaluated for diethylene glycol (DEG) exposures. The primary objective of this study was to evaluate the utility of the OG in estimating DEG serum concentrations using the most common formula that is currently used for estimating methanol, ethanol, and ethylene glycol concentrations.METHODS:This was a controlled laboratory investigation using serum samples individually spiked with a known quantity of toxic alcohol compared to no toxic alcohol. Test samples were spiked with ethanol, DEG, EG, and methanol. Serum chemistries and osmolality and osmolarity were determined, and the OG was determined for each specimen.RESULTS:The percent error of estimating DEG concentrations of 26.3％ was similar to the mean percent error for estimating other alcohol concentrations, 30.5％±5.6％ (P>0.05, 95％ confidence interval 16.7％-44.3％).CONCLUSIONS:The severity of metabolic effects associated with DEG and the need to appropriately determine rescue treatments mandate early detection of significant exposures for effective triage and patient management. Our results indicate that the percent error of the osmol gap method for estimating DEG concentration is similar to that of other toxic alcohols; this simple technique could be a valuable clinical tool, since quantitative DEG analysis is rarely available.