Acid-Base & ElectrolytesEvidence-Based Golden Standard
Delta Gap & Delta-Delta Ratio (ΔAG / ΔHCO₃⁻)
Evaluates complex mixed acid-base disorders in high anion gap metabolic acidosis (HAGMA) by comparing the change in anion gap to the change in bicarbonate.
ΔAG = Anion Gap - 12
ΔHCO₃⁻ = 24 - HCO₃⁻
Delta Ratio = ΔAG / ΔHCO₃⁻
Published Clinical Benchmark Cases
Clinical Parameters & Inputs
Unit: mEq/L
mEq/L
Unit: mEq/L
mEq/L
Unit: mEq/L
mEq/L
Standard textbook normal is 12 mEq/L (range 10-14).
Unit: mEq/L
mEq/L
Standard textbook normal is 24 mmol/L.
Computed OutputPure Uncomplicated HAGMA
1.2
Diagnostic Interpretation
Delta Ratio between 0.8 and 2.0 (1.2). Demonstrates an uncomplicated, pure High Anion Gap Metabolic Acidosis where 1 mmol of unmeasured acid anion buffers approximately 1 mmol of bicarbonate (e.g. uncomplicated DKA or acute lactic acidosis).
Calculation Breakdown
Delta Anion Gap (ΔAG)
24 - 12 =12 mEq/L
Delta Bicarbonate (ΔHCO₃⁻)
24 - 14 =10 mmol/L
Delta Ratio (ΔAG / ΔHCO₃⁻)
12 / 10 =1.2
Clinical Decision Pearls
- A ratio < 0.8 alerts the clinician to an unexpected concurrent NAGMA (e.g. saline-induced hyperchloremia during DKA resuscitation).
- A ratio > 2.0 alerts the clinician to an unexpected concurrent metabolic alkalosis (e.g. severe vomiting preceding DKA).
Limitations & Confounders
- The ratio assumes a standard baseline anion gap of 12 and HCO3 of 24. If patient baseline values were abnormal before acute illness, interpretation must be adjusted.
Evidence & Citations
- Wrenn K. The delta (Δ) gap: an approach to mixed acid-base disorders. Ann Emerg Med. 1990;19(11):1310-1313.
- Kraut JA, Madias NE. Serum anion gap: its uses and limitations in clinical medicine. Clin J Am Soc Nephrol. 2007;2(1):162-174.