Which method of analysis will provide the most accurate electrolyte results if a grossly lipemic sample is used?

Which method of analysis will provide the most accurate electrolyte results if a grossly lipemic sample is used?

• A. Direct ISE
• B. Indirect ISE
• C. Flame emission photometry
• D. Atomic absorption

Answer: (A)

Direct ISE is best for lipemic samples because it measures electrolyte activity directly in undiluted plasma, avoiding any dilution step. Indirect ISE dilutes the sample, and the lipid particles reduce the aqueous fraction of plasma; this artificial lowering of the water phase makes the measured electrolyte concentration falsely low (pseudohyponatremia) and less reliable in lipemia. The other methods aren’t appropriate for routine electrolyte analysis in this context: flame emission photometry and atomic absorption aren’t standard for measuring the common electrolytes in plasma, and they don’t offer the direct, dilution-free measurement that preserves accuracy when lipids are present.

Direct ISE is best for lipemic samples because it measures electrolyte activity directly in undiluted plasma, avoiding any dilution step. Indirect ISE dilutes the sample, and the lipid particles reduce the aqueous fraction of plasma; this artificial lowering of the water phase makes the measured electrolyte concentration falsely low (pseudohyponatremia) and less reliable in lipemia. The other methods aren’t appropriate for routine electrolyte analysis in this context: flame emission photometry and atomic absorption aren’t standard for measuring the common electrolytes in plasma, and they don’t offer the direct, dilution-free measurement that preserves accuracy when lipids are present.