American Board of Internal Medicine (ABIM) Certification Practice Exam

What condition can lead to pseudohyponatremia due to laboratory measurement errors?

1. Hyperlipidemia

2. Acute kidney injury

3. Dehydration

4. Chronic kidney disease

The correct answer is: Hyperlipidemia

Pseudohyponatremia occurs when the measured serum sodium level is falsely low due to the presence of certain substances in the blood that interfere with laboratory measurements. Hyperlipidemia is known to cause pseudohyponatremia because a high concentration of lipids can lead to a dilution effect on the sodium concentration measured by various laboratory techniques, particularly when using indirect ion-selective electrodes. This results in an inaccurately low serum sodium reading without an actual deficiency in the sodium content of the body. In contrast, conditions like acute kidney injury, dehydration, and chronic kidney disease typically lead to genuine changes in sodium levels or alterations in fluid status without causing the laboratory measurement artifact seen in pseudohyponatremia. While these conditions can certainly affect sodium balance and result in true hyponatremia, they are not characterized by the same measurement errors associated with hyperlipidemia.