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To the Editor.—
In a recent issue of The Journal, Goldstein et al commented on the usefulness of ascertaining if a low anion gap is present. The comment that only one case of multiple myeloma was found out of a total of 39,360 retrospective electrolyte determinations would suggest that this quest would lack utility. If one, however, notes that out of the 19 patients who had verification of a low anion gap by repeated determinations, 16 could be explained by either hypoalbuminemia or hyponatremia, the astute mathematician realizes that one third of the remaining patients had multiple myeloma. Therefore, if hypoalbuminemia and hyponatremia are ruled out, the incidence of multiple myeloma in patients who have verified low anion gaps in this study is 33%. There are few such noninvasive laboratory tests that have this degree of specific diagnostic value.It would be more interesting to know how many of the
Mitnick PD. The Low Anion Gap. JAMA. 1980;244(18):2047. doi:10.1001/jama.1980.03310180017018