What is measured to determine the anion gap?

The anion gap is a calculated value used primarily to help identify the cause of metabolic acidosis. It reflects the difference between the concentrations of positively charged ions (cations) and negatively charged ions (anions) in the serum. The primary ions measured to determine the anion gap are sodium (Na+), chloride (Cl-), and bicarbonate (HCO3-).

In this calculation, sodium is typically the main cation, while the anions are represented by the sum of chloride and bicarbonate concentrations. The formula is commonly expressed as:

Anion Gap = Na+ - (Cl- + HCO3-)

This measurement assists healthcare providers in diagnosing conditions related to acid-base balance, such as metabolic acidosis, and can guide further testing and management. Other options, while they involve important physiological parameters, do not contribute to the calculation of the anion gap.