In a lipemic sample measured for Na+ by indirect ISE, the reported Na+ is most likely which artifact?

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Multiple Choice

In a lipemic sample measured for Na+ by indirect ISE, the reported Na+ is most likely which artifact?

The key idea is how indirect ISE measurements handle samples with unusual solid content, like lipids. Indirect ISE dilutes the plasma before measuring sodium and assumes a normal proportion of plasma water. Lipemia, with many lipids dispersed in plasma, reduces the actual aqueous water fraction that contains the sodium. When you dilute a sample with less water, the sodium concentration reported per liter of whole plasma appears lower than it truly is, even though the total body sodium is normal. This creates a falsely low sodium reading—pseudohyponatremia. Other options aren’t the artifact produced by lipemia in indirect ISE measurements: true hypernatremia would imply excess sodium in reality, which lipemia does not cause; hyponatremia due to dilution describes a physiological situation rather than an analytical artifact from the measurement method; and pseudonormonatremia isn’t a recognized artifact in this context.

The key idea is how indirect ISE measurements handle samples with unusual solid content, like lipids. Indirect ISE dilutes the plasma before measuring sodium and assumes a normal proportion of plasma water. Lipemia, with many lipids dispersed in plasma, reduces the actual aqueous water fraction that contains the sodium. When you dilute a sample with less water, the sodium concentration reported per liter of whole plasma appears lower than it truly is, even though the total body sodium is normal. This creates a falsely low sodium reading—pseudohyponatremia.

Other options aren’t the artifact produced by lipemia in indirect ISE measurements: true hypernatremia would imply excess sodium in reality, which lipemia does not cause; hyponatremia due to dilution describes a physiological situation rather than an analytical artifact from the measurement method; and pseudonormonatremia isn’t a recognized artifact in this context.

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