Which test measures the concentration of sodium in serum?

• A. Pulmonary Angiography
• B. Sodium Levels
• C. Sigmoidoscopy
• D. Thoracentesis

Answer: (B)

Measuring the concentration of sodium in serum is done with a blood test that reports serum sodium levels, typically as part of an electrolyte panel. This test directly analyzes the amount of sodium ions circulating in the blood, usually expressed in mEq/L, and helps assess hydration, kidney function, and electrolyte balance.

Pulmonary angiography is an imaging test that visualizes the lung blood vessels. Sigmoidoscopy is a procedure to inspect the lower part of the colon. Thoracentesis involves removing fluid from the pleural space for analysis. None of these measure the sodium concentration in serum, so they’re not used to determine serum sodium levels.