Anion Gap Other Than Metabolic Acidosis

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