title: The anion gap and routine serum protein measurements in monoclonal gammopathies.
abstract: OBJECTIVE
  An abnormal anion gap and an increased total protein and globulin are clues to the diagnosis of monoclonal gammopathy. We explored the utility of these markers in IgG, IgA, IgM, and free light chain monoclonal gammopathies.
  
  
  METHODS
  The anion gap, Na(+) - (Cl(-) + HCO(3)(-)), corrected for hypoalbuminemia, was calculated in patients with monoclonal gammopathies. Exclusion criteria were serum calcium >10.5 mg/dl and/or creatinine >2 mg/dl.
  
  
  RESULTS
  Among 287 patients, 242 remained after applying exclusion criteria (109 IgG, 64 IgA, 21 IgM, and 48 light chain); 36% of 242 patients required correction for hypoalbuminemia. The anion gap was decreased (<10) in 22% of IgG and increased (>15) in 31% of IgA monoclonal gammopathies. IgM did not affect the gap. In light chain gammopathies, the anion gap showed no consistent trend (15% increased, 17% decreased). Mean clonal IgG, IgA, and IgM concentrations were 10-fold higher than mean clonal free light chain concentrations in the respective monoclonal gammopathies (P < 0.001). These paraprotein level disparities were reflected in significantly increased mean serum total protein and globulin concentrations in IgG, IgA, and IgM versus free light chain monoclonal gammopathies, where mean total protein and globulin levels were within normal limits (P < 0.001).
  
  
  CONCLUSIONS
  The anion gap was significantly altered in IgG and IgA monoclonal gammopathies, but it was not a sensitive tool for suspecting the diagnosis. In light chain monoclonal gammopathies, the anion gap, total protein, and globulin did not provide reliable diagnostic clues.
authors.affiliation: The Binding Site, Inc.,San Diego, California, USA. karvanhoev@aol.com
authors.forename: Karen H
authors.initials: KH
authors.lastname: van Hoeven
authors.forename: Rosy E
authors.initials: RE
authors.lastname: Joseph
authors.forename: William J
authors.initials: WJ
authors.lastname: Gaughan
authors.forename: Laura
authors.initials: L
authors.lastname: McBride
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Bilotti
authors.forename: Ann
authors.initials: A
authors.lastname: McNeill
authors.forename: Linda
authors.initials: L
authors.lastname: Schmidt
authors.forename: Danielle
authors.initials: D
authors.lastname: Schillen
authors.forename: David S
authors.initials: DS
authors.lastname: Siegel
mesh_terms: D000136:Acid-Base Equilibrium; D000328:Adult; D000368:Aged; D001798:Blood Proteins / Q000032:analysis*; D005260:Female; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis; D008297:Male; D008875:Middle Aged; D010265:Paraproteinemias / Q000378:metabolism*; D012189:Retrospective Studies
chemical_list: D001798:Blood Proteins; D007136:Immunoglobulins