Which constituent normally present in serum must be eliminated to avoid interference with serum magnesium measurement?

Which constituent normally present in serum must be eliminated to avoid interference with serum magnesium measurement?

• A. Calcium
• B. Chloride
• C. Iron
• D. Potassium

Answer: (A)

Calcium interference is the issue in this magnesium measurement. In many serum magnesium assays, a dye forms a colored complex specifically with Mg2+. Calcium, present in relatively high levels in serum, can bind the same dye or otherwise compete for the reagent, altering the color change and skewing the result. To get an accurate Mg2+ reading, calcium must be removed or masked from the sample before the assay. The other ions listed don’t interact with the magnesium-dye complex to the same extent, so they don’t necessitate removal for this measurement.

Calcium interference is the issue in this magnesium measurement. In many serum magnesium assays, a dye forms a colored complex specifically with Mg2+. Calcium, present in relatively high levels in serum, can bind the same dye or otherwise compete for the reagent, altering the color change and skewing the result. To get an accurate Mg2+ reading, calcium must be removed or masked from the sample before the assay. The other ions listed don’t interact with the magnesium-dye complex to the same extent, so they don’t necessitate removal for this measurement.