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Harmonisation of Osmolal Gap - Can We Use a Common Formula?
Kay Weng Choy1, Nilika Wijeratne2, Zhong X Lu3
1Department of Pathology, Monash Medical Centre, Clayton, Vic., 3168, Australia.
The Clinical Biochemist. Reviews
|November 23, 2016
Summary
The osmolal gap identifies unmeasured substances in the blood. The Smithline-Gardner formula [2(Na) + Glu + Urea] is recommended for accurate osmolal gap calculation in clinical settings.
Area of Science:
- Clinical Chemistry
- Medical Diagnostics
Background:
- The osmolal gap quantifies unmeasured osmotically active particles in serum.
- Its primary clinical utility lies in screening for toxic substance ingestion in emergency and intensive care settings.
Approach:
- This study reviews historical and proposed formulas for osmolal gap calculation.
- It evaluates the 'fitness for purpose' based on accuracy, precision, and platform variability.
- The Smithline-Gardner formula [2(Na) + Glu + Urea] is identified as a robust option.
Key Points:
- Osmolal gap uncertainty arises from errors in measured and calculated osmolality, plus unmeasured analytes.
- The Smithline-Gardner formula demonstrates suitability across diverse patient populations and analytical platforms.
- This formula allows for both rapid bedside estimation and automated laboratory reporting.
Conclusions:
- The Smithline-Gardner formula is proposed for universal adoption due to its reliability and ease of use.
- Standardizing osmolal gap calculation enhances diagnostic consistency in clinical practice.
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