What goes into the Anion gap and delta ratio
- Sodium (mEq/L)
- Chloride (mEq/L)
- Bicarbonate (mEq/L)
- Albumin (optional) (g/dL)
- pCO₂ (optional) (mmHg)
How to interpret the result
- Anion gap = Na − (Cl + HCO₃); normal about 8–12 mEq/L (check your lab's range)
- Albumin-corrected gap adds 2.5 for every 1 g/dL that albumin is below 4
- Delta ratio < 0.4 normal-gap acidosis; 0.4–1 mixed; 1–2 pure high-gap acidosis; > 2 concurrent metabolic alkalosis
- Winter's expected pCO₂ = 1.5 × HCO₃ + 8 ± 2; above it means respiratory acidosis, below it respiratory alkalosis
Clinical pearls
- High anion gap causes include lactate, ketones (DKA, alcohol, starvation), toxic alcohols, salicylates and uremia.
- Hypoalbuminemia hides a raised gap unless you correct for it.
Evidence
- Albert MS, Dell RB, Winters RW. Quantitative displacement of acid-base equilibrium in metabolic acidosis. Ann Intern Med. 1967;66:312-322.
- Figge J, et al. Anion gap and hypoalbuminemia. Crit Care Med. 1998;26:1807-1810.
Related workups
Related calculators
For education only. Check the inputs and the population the score was validated in before acting on it. Not a substitute for clinical judgment.