Interpretation
| Result | Meaning |
|---|---|
| ≤ 0 | No excess anion gap |
| Δgap ≈ (24 − HCO₃) | Pure high-gap acidosis |
| Δgap > (24 − HCO₃) | Plus metabolic alkalosis |
| Δgap < (24 − HCO₃) | Plus normal-gap acidosis |
Formula
Corrected AG = Na⁺ − (Cl⁻ + HCO₃⁻) + 2.5 × (4 − albumin g/dL). Albumin-corrected delta gap = corrected AG − 12. Mixed-disorder check: corrected HCO₃ = HCO₃ + Δgap (>26 alkalosis, <22 added normal-gap acidosis).
Clinical pearls
- Every 1 g/dL fall in albumin lowers the anion gap by about 2.5 mmol/L; uncorrected gaps miss acidoses in hypoalbuminaemic ICU patients.
- Use your lab's normal anion gap: with ion-selective electrodes the normal AG may be nearer 8–10, which shifts the delta gap.
- Matches the MedCalc-Bench definition (normal AG 12, normal albumin 4 g/dL, factor 2.5). The mixed-disorder thresholds (corrected HCO₃ 22–26) are the conventional teaching rule.
Examples
albumin corrected delta gap na 140 cl 100 hco3 14 albumin 2.0corrected delta gap: sodium 137, chloride 104, bicarb 18, alb 4what is the delta gap corrected for albumin 25 g/L, Na 140, Cl 98, HCO3 26
FAQ
Why correct the delta gap for albumin?
Albumin is the main unmeasured anion. Hypoalbuminaemia lowers the anion gap, so without correction a real gap acidosis can look normal and the delta gap is underestimated.
How is the delta gap used?
Compare the rise in anion gap with the fall in bicarbonate. If the gap rose much more than the bicarbonate fell, there is also a metabolic alkalosis; if much less, there is also a normal-gap acidosis.