Generation of an osmolality gap-ethanol nomogram from routine laboratory data

Area of Science:

• Clinical Chemistry
• Laboratory Medicine
• Toxicology

Background:

• The osmolality gap is a critical indicator in diagnosing conditions like alcohol intoxication.
• Existing nomograms for osmolality gap and serum ethanol may not align with diverse laboratory methodologies.
• Interlaboratory analytical bias and formula selection impact the accuracy of published nomograms.

Purpose of the Study:

• To develop a practical, adaptable procedure for generating laboratory-specific nomograms.
• To describe the relationship between osmolality gap and serum ethanol concentrations.
• To ensure nomogram relevance across different analytical methods and formulas.

Main Methods:

• Retrospective analysis of patient data including serum sodium, glucose, urea nitrogen, ethanol, and osmolality.
• Utilized spreadsheet software for nomogram generation.
• Employed regression analysis and truncated normal distributions for nomogram refinement.

Main Results:

• Published nomograms and common criteria showed significant inconsistencies with laboratory data.
• A novel nomogram, derived from regression analysis, better represented the collected data.
• The developed nomogram is tailored to specific laboratory formulas and analytical methodologies.

Conclusions:

• Laboratory-specific nomograms are essential due to interlaboratory variability and formula choices.
• The described spreadsheet procedure enables laboratories to create their own nomograms.
• This method avoids the need for measuring volatiles other than ethanol, simplifying the process.