Anion Gap & Delta-Delta
Anion Gap & Delta-Delta - a deterministic tool in Sophie Well's Clinical Math & Conversions group.
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What this is
Compute the serum anion gap (Na - (Cl + HCO3)), albumin-correct it when albumin is below 4 g/dL, and run the delta-delta ratio to decide whether a high-gap metabolic acidosis is pure or mixed with a concurrent non-gap process or a metabolic alkalosis. Sophie Well returns the raw gap, the corrected gap, the delta gap, and the delta ratio with the standard interpretation bands (<0.4 concurrent non-gap acidosis; 0.4-1.0 mixed; 1.0-2.0 pure HAGMA; >2.0 concurrent metabolic alkalosis).
When to use it
Use this when reading a basic metabolic panel that shows an elevated gap and you want to know whether one acid-base process explains the picture or whether two or three are running at once. The delta-delta is the cheapest way to detect a mixed disorder that the gap alone hides. The numbers do not name the acid - MUDPILES still requires a clinical workup - but they tell you whether to look for a single culprit or to keep widening the differential.
References
Standard chemistry references; Wrenn KD. The delta gap. Ann Emerg Med. 1990;19(11):1310-1313.
Worked example: AG 26; delta-AG 14; delta-HCO3 10; ratio 1.4 - pure AG metabolic acidosis
Sophie Well is a reference and educational tool. Not medical, legal, or financial advice. Does not replace clinician judgment, professional billing review, or legal counsel.