The anion gap is useful for quality control of laboratory results for which parameter set?

• A. Amino Acids and Proteins
• B. Blood Gas Analyzers
• C. Na, K, Cl, and CO2
• D. Ca, Ph, Mg

Answer: (C)

Anion gap serves as a quick quality check on the electrolyte measurements. It is calculated as sodium minus the sum of chloride and bicarbonate (often reported as CO2 on analyzers). A normal gap indicates the Na, Cl, and CO2 results are consistent with each other, helping to flag analytical or preanalytic issues if the value is abnormal. Since the calculation relies on Na, Cl, and CO2, it directly applies to the electrolyte parameter set that includes those measurements (Na, Cl, and CO2). Potassium may be included in the panel for completeness, but it does not affect the gap calculation. The other parameter groups do not use the anion gap for quality control.