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Serum calcium levels are often interpreted relative to serum albumin levels because calcium in the blood is largely bound to albumin. Here's how it is typically done:

1. Total serum calcium measurement: 

The laboratory measures the total serum calcium level, which includes both the bound (albumin-bound) and free (ionized) calcium in the blood.

2. Serum albumin measurement: 

The laboratory also measures the serum albumin level, which indicates the amount of albumin present in the blood.

3. Corrected calcium calculation:

If the serum albumin level is abnormal (either low or high), a corrected calcium calculation is performed to account for the binding of calcium to albumin. The corrected calcium level is an estimate of the calcium level that would be present if the albumin level were within the normal range.

4. Corrected calcium formula: 

The most commonly used formula to calculate corrected calcium is as follows:
Corrected Calcium (mg/dL) = Total Serum Calcium (mg/dL) + 0.8 x (4 - Serum Albumin [g/dL])
Note: This formula assumes that each 1 g/dL decrease in serum albumin below 4 g/dL corresponds to a 0.8 mg/dL decrease in the total serum calcium level.

5. Interpretation of corrected calcium: 

The corrected calcium level is then interpreted based on established reference ranges. The interpretation takes into account the patient's clinical condition, symptoms, and other relevant factors.

It's important to note that the corrected calcium level is an estimate and may not precisely reflect the ionized calcium level, which is the biologically active form of calcium. In some cases, direct measurement of ionized calcium may be necessary for accurate assessment.