Elevated lipid levels interfere with indirect ISE by causing which change in sodium results?

Elevated lipid levels interfere with indirect ISE by causing which change in sodium results?

• A. Falsely increased
• B. Falsely decreased
• C. No effect
• D. Unpredictable results

Answer: (B)

Elevated lipids change how indirect ISE measures sodium because this method dilutes the serum and assumes a constant water fraction in plasma. When lipids (and other non-aqueous components) rise, the actual water portion of plasma decreases. Sodium sits in this aqueous phase, so diluting a sample with less water results in a lower measured sodium concentration. This creates a falsely decreased sodium result, known as pseudohyponatremia. Direct ISE, which analyzes undiluted samples, is less affected by lipemia.

Elevated lipids change how indirect ISE measures sodium because this method dilutes the serum and assumes a constant water fraction in plasma. When lipids (and other non-aqueous components) rise, the actual water portion of plasma decreases. Sodium sits in this aqueous phase, so diluting a sample with less water results in a lower measured sodium concentration. This creates a falsely decreased sodium result, known as pseudohyponatremia. Direct ISE, which analyzes undiluted samples, is less affected by lipemia.