Decreased anion gap associated with hypoalbuminemia and polyclonal gammopathy.

Anion gaps were determined in 82 patients with hypoalbuminemia; 24 of these patients had a polyclonal increase in gamma-globulin levels (designated group 5). The 58 patients without the polyclonal increase in gamma-globulin levels were subdivided according to the origin of their serum albumin loss as follows: group 1, renal group 2, gastrointestinal; group 3, skin; and group 4, malignant neoplasms. All groups had a statistically significant reduction in their mean anion gaps when compared with normal control subjects. The greatest decrease was when hypoalbuminemia was accompanied by a polyclonal increase in gamma-globulin levels. Hypoalbuminemia with or without a polyclonal gammopathy is a cause of a low anion gap. No statistically significant correlation was found between the anion gaps and individual serum albumin concentrations.