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- Title
Diagnostic accuracy of osmolal gap, anion gap, and acidosis for methanol, ethylene glycol, and isopropanol testing in Calgary: A review of current practice and evaluation of laboratory predictors.
- Authors
Thommasen, Amy T.; Naugler, Christopher; Yarema, Mark; Seiden-Long, Isolde
- Abstract
Objective: Investigate (1) the diagnostic utility of osmolal gap (OGAP) as a screening test for serum methanol, ethylene glycol, and isopropanol exposure and (2) the effect of ethanol correction, anion gap (AGAP) and pH on the accuracy of OGAP. Methods: All patient encounters where serum methanol, ethylene glycol, and isopropanol were ordered between January 2013 and June 2014 from 5 hospitals and 4 health centres in Calgary, Alberta, were collected. A correction coefficient for serum ethanol in OGAP was calculated by linear regression. The diagnostic accuracy of OGAP, serum pH and AGAP to identify patients with any detectable serum methanol, ethylene glycol, or isopropanol concentration was analyzed using sensitivity, specificity, odds ratio, multivariate receiver operator curves, and decision trees using SPSS software. Data and results: Seventy-nine of 886 encounters had detectable serum methanol, ethylene glycol, or isopropanol concentrations. A coefficient of 1.1 best corrected for ethanol contribution to measured serum osmolality. The resulting OGAP equation (OGAP = osmolalitymeasured - (2*sodium+glucose+UREA+Ethanol*1.1) had a sensitivity and specificity of 89% and 54%, respectively, above a threshold of =10. OGAP, serum ethanol, and arterial or venous pH had signifcant odds ratios to any detectable serum toxic alcohol. The area under the curve (AUC) for OGAP alone (AUC= 0.67) was improved by ethanol (AUC= 0.85) and ethanol and pH (AUC=0.91) (p<0.001 in all comparisons). Conclusions: OGAP is a sensitive but non-specific test at a decision threshold of 10 that is improved by consideration of serum ethanol, AGAP and pH in evaluation of suspected toxic alcohol ingestion.
- Publication
Canadian Journal of Pathology, 2016, Vol 8, p31
- ISSN
1918-915X
- Publication type
Article