American Board of Internal Medicine (ABIM) Certification Practice Exam

How much does total calcium decline for each 1.0 g/dL decrease in serum albumin concentration?

1. 0.5 mg/dL

2. 0.8 mg/dL

3. 1.0 mg/dL

4. 1.5 mg/dL

The correct answer is: 0.8 mg/dL

When serum albumin concentration decreases, there is an impact on total calcium levels in the body. This is because a significant portion of calcium in the blood is bound to proteins, primarily albumin. When albumin levels drop, the bound calcium decreases, leading to a reduction in the measured total calcium concentration. Clinical guidelines suggest that for each 1.0 g/dL decrease in serum albumin, total calcium levels typically decline by approximately 0.8 mg/dL. This adjustment is important in clinical practice since total calcium levels can be misleading if not considered in the context of the serum albumin concentration. Understanding this relationship helps healthcare professionals accurately interpret calcium levels and address any potential imbalances, ensuring that patients receive appropriate treatment for conditions related to calcium metabolism or abnormalities in protein levels.