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The fall of the serum anion gap
S D Winter1, J R Pearson, P A Gabow
1Clinical Laboratory, Denver General Hospital, Colo 80204-4507.
Archives of Internal Medicine
|February 1, 1990
Summary
The traditional anion gap reference range of 8 to 16 mmol/L may be outdated due to modern analyzers. New reference ranges, like 3 to 11 mmol/L, are suggested for accurate diagnosis of acid-base disorders.
Area of Science:
- Clinical Chemistry
- Electrolyte Analysis
- Diagnostic Medicine
Background:
- The anion gap is a calculated value used to assess acid-base balance.
- Current reference ranges for the anion gap may not reflect advancements in analytical technology.
Purpose of the Study:
- To evaluate the current reference range for serum anion gap using modern electrode technology.
- To determine the validity of the commonly used 8 to 16 mmol/L reference range.
Main Methods:
- Electrolyte measurements were performed using a Beckman ASTRA analyzer.
- Serum samples from healthy volunteers (n=29) and blood donors (n=120) were analyzed.
- Aqueous standards were used for verification against National Bureau of Standards reference material.
Main Results:
- A downward shift in the anion gap reference range was observed, with values potentially falling between 3 to 11 mmol/L.
- Modern analyzers typically yield lower anion gap values (≤6 mmol/L) in normal individuals.
- An upward shift in chloride values was identified as the primary reason for the decreased anion gap.
Conclusions:
- The traditional anion gap reference range requires re-evaluation with new instrumentation.
- Clinicians must be aware of updated reference ranges for effective diagnosis of acid-base disorders.
- Anion gap interpretation needs to adapt to technological advancements in electrolyte analysis.
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