Decreased anion gap in polyclonal hypergammaglobulinemia

Objectives: The anion gap has proved a valuable tool in the diagnosis of various forms of acid-base disorders, although the importance of slight rises in the anion gap remains unclear. The concept of the anion gap is often misunderstood and misapplied. The relationship between gammaglobulins and the serum anion gap has not received much attention except for reports of a narrowing of the gap associated with certain monoclonal immunoglobulin G gammopathies. We present patients with polyclonal gammopathy, the magnitude of which correlated strongly and negatively with the anion gap. Design: The anion gap can be readily calculated from routine laboratory data, and anion gap was calculated as ([Na] +[K])- ([Cl] + [HCO3]). Subjects: Serum anion gaps were determined in 206 patients with polyclonal hypergammaglobulinemia and 63 healthy subjects. Measurements: Serum sodium and potassium ions concentration were determined by flame photometry. Serum bicarbonate level was measured as total carbon dioxide content. Serum chloride level was determined by chlorimetric titration with silver ions. Results: All patients with polyclonal hypergammaglobulinemia had a statistically significant reduction in their mean serum anion gaps (6.4 ± 1.2 mmol/L) when compared with normal control volunteers (15.3 ± 2.4 mmol/L), p< 0.05. Conclusions: Our results show a negative correlation between serum anion gap and gammaglobulins concentration.