An attending physician is evaluating a hospitalized patient who has developed worsening lower extremity edema and frothy urine. Initial laboratory studies reveal a serum albumin level of g/dL. A basic metabolic panel is obtained concurrently, which demonstrates a measured total serum calcium level of mg/dL. Assuming a standard reference albumin value of g/dL for calculation purposes, what is this patient's corrected total serum calcium concentration?
Answer: 8.8 mg/dL
Answer
The corrected total serum calcium concentration is 8.8 mg/dL.
The correct calculation yields 8.8 mg/dL. Approximately 40% to 45% of total serum calcium is bound to plasma proteins, primarily albumin. When albumin levels are significantly reduced (such as in nephrotic syndrome), the measured total calcium drops accordingly. However, the physiologically active ionized calcium generally remains normal. To avoid erroneously diagnosing true hypocalcemia (pseudohypocalcemia), the measured total calcium must be corrected by adding 0.8 mg/dL for every 1.0 g/dL decrease in serum albumin below the standard reference of 4.0 g/dL. In this patient, the albumin deficit is 2.5 g/dL, resulting in an upward correction of 2.0 mg/dL to the measured 6.8 mg/dL.
Step-by-Step Solution
Key Concept
Correcting total serum calcium in the setting of hypoalbuminemia to distinguish true hypocalcemia from pseudohypocalcemia.
Estimated Time:1m 0s