What is the correct expression for the anion gap as described in the material?

What is the correct expression for the anion gap as described in the material?

• A. Na + K - (Cl + HCO3)
• B. Na - Cl - HCO3
• C. (Na + Cl) - (K + HCO3)
• D. Na + K + Cl + HCO3

Answer: (A)

Anion gap comes from comparing the major measured cations with the major measured anions in blood to estimate unmeasured anions. The typical measured cations are sodium and potassium, while the main measured anions are chloride and bicarbonate. Subtracting the sum of the major anions from the sum of the major cations gives the expression Na + K - (Cl + HCO3). This difference reflects unmeasured negatively charged substances such as albumin, phosphate, sulfate, and lactate. If potassium isn’t included, the expression simplifies to Na - (Cl + HCO3). For example, with Na 140, K 4, Cl 100, and HCO3 24, the anion gap is 20.

Anion gap comes from comparing the major measured cations with the major measured anions in blood to estimate unmeasured anions. The typical measured cations are sodium and potassium, while the main measured anions are chloride and bicarbonate. Subtracting the sum of the major anions from the sum of the major cations gives the expression Na + K - (Cl + HCO3). This difference reflects unmeasured negatively charged substances such as albumin, phosphate, sulfate, and lactate. If potassium isn’t included, the expression simplifies to Na - (Cl + HCO3). For example, with Na 140, K 4, Cl 100, and HCO3 24, the anion gap is 20.