Anion Gap(K⁺)

Definition
Anion Gap(K⁺) is the concentration difference between the cations, sodium and potassium, and the measured anions, chloride and bicarbonate.

Anion Gap(K⁺) = cNa⁺ + cK⁺ - cCl^– - cHCO^-₃.

The systematic symbol is Anion Gap(K⁺). The analyzer symbol may be Anion Gap(K⁺).

What does Anion Gap(K⁺) tell you
Anion Gap(K⁺) is a reflection of the unmeasured anions in the plasma, e.g., proteins, organic acids, sulfates, and phosphates (although changes in plasma calcium and magnesium also affect the Anion Gap(K⁺)).
Anion Gap(K⁺) may be an aid in the differential diagnosis of metabolic acidosis. Metabolic acidosis can be classified in two groups:    

1. Those with an increase in Anion Gap(K⁺), thus implying the presence of increased amounts of organic acid.
2. Those with normal Anion Gap(K⁺), due to loss of bicarbonate.

Reference ranges
Anion Gap(K⁺) reference range (adult): 10-20 mmol/L
disclaimer

Clinical interpretation

A. Decreased Anion Gap(K⁺) can be caused by:

• Decrease in plasma proteins
• Hyponatriemia
• Increase in unmeasured cations

B. Increased Anion Gap(K⁺) can be caused by:

• Ketoacidosis
• Lactoacidosis
• Renal failure
• Intoxication with: salicylate, methanol, and ethylene glycol

C. Metabolic acidosis with a normal Anion Gap(K⁺):

• Diarrhea
• Uremic acidosis of recent onset
• Renal tubular acidosis