November 21, 1990

What Matters Magnesium?

Author Affiliations

Harvard Medical School New England Deaconess Hospital Boston, Mass

Harvard Medical School New England Deaconess Hospital Boston, Mass

JAMA. 1990;264(19):2502. doi:10.1001/jama.1990.03450190031014

To the Editor.—  The recent article by Whang and Ryder1 recommends the addition of magnesium measurements to the standard electrolyte profile. This recommendation is based on their finding that a large number of serum specimens drawn for electrolyte determinations had magnesium concentrations outside the published range of normal.This article does not appear to report the actual number of patients in whom an abnormal serum magnesium level was missed, but rather the number of blood specimens with abnormalities. Although the "Methods" section is not detailed enough to be conclusive, it seems plausible that substantial double-counting occurred. If, for example, a physician ordered electrolyte analyses five times on a single patient during the 12 days of the study, and the serum magnesium level was abnormal each time, the authors would have reported five "missed" abnormal magnesium levels. Given that sick, hospitalized patients are more likely to have both magnesium abnormalities