What is the formula for corrected serum calcium?

The formula for corrected serum calcium is essential in assessing calcium levels accurately, especially in patients with low serum albumin levels. The correct formula, which is presented in the chosen option, accounts for the concentration of albumin in the blood.

In this formula, the term [(4-albumin)x0.8] calculates the expected increase in calcium for every 1 g/dL decrease in albumin below the normal level of 4 g/dL. This adjustment is necessary because calcium binding to albumin can affect the total serum calcium level. The addition of the actual measured serum calcium helps in determining the corrected serum calcium level, which provides a more accurate assessment of the physiologically active calcium in the body.

This correction is particularly relevant in elderly individuals or those with conditions that can cause hypoalbuminemia, thus making serum calcium levels potentially misleading if not adjusted. The chosen formula elegantly incorporates the relationship between calcium and albumin, making it a vital tool in gerontological nutrition and care for older adults.