The Low Anion Gap

To the Editor.— The article by Goldstein et al on the anion gap provides a comprehensive summary of the range of anion gap in a hospitalized population, but some of the conclusions that the authors draw may not necessarily be justified by the data.

The authors assembled the data on anion gap in a large number of hospitalized patients, obtained a mean ±2 SDs, assumed that values below this range are low, and found only a few patients with a low anion gap. However, the appropriate comparison would have been with the range of anion gap found in a healthy population. A number of studies have shown that the range found in a healthy population is narrower than the range found in hospitalized patients (as reviewed by Witte et al¹). It is obvious that the high values in hospital patients will include those in renal failure and other forms