Conventionally Serum Anion Gap is calculated as:
Serum AG = Na - (Cl + HCO3)
- Na is Primary Cation
- CL+HCO3 are Primary Anion
Serum AG = All unmeasured anions – all unmeasured cations
What are Unmeasure Anions?
- Any ion in the serum other than Na, Cl, or HCO3
Causes of lower Serum AG
•Hypoalbumin
•Hyperkalemia
•Hypercalcemia
•Hypermagnesemia
•Lithium toxicity
•IgG multiple myeloma
Negative Serum AG:
- Rarely seen.
- Laboratory error ( this is not reproducible)
- Overestimation of serum chloride: marked hyperlipidemia, salicylate intoxication, bromide intoxication ( in past bromide used as sedative
