title: Anion gap among patients of multiple myeloma and normal individuals.
abstract: OBJECTIVE
  To compare the Anion gap between patients of multiple myeloma and normal individuals presenting at a tertiary care hospital.
  
  
  METHODS
  This is a matched case-control study conducted at Aga Khan University Hospital, Karachi, from July 10, 2004 to April 30, 2006. The anion gap (AG) from the medical records of the 82 diagnosed cases of multiple myeloma (MM) and 104 controls were compared. Immunoglobulins (IgG and IgA) were measured by array nephelometric assay. Staging for MM patients were performed based on Salmon-Durie method. AGs were compared by independent sample t-test. Pearson coefficient of correlation was used to correlate paraprotein IgG concentration and anion gap.
  
  
  RESULTS
  : Of the 186 study subjects (82 cases and 104 controls), 70% were males and 30% were females. The mean ages of MM and controls were 59.68+/-11.94 and 60+/-9.2 years respectively. There was a significant difference in mean AG, 11.2+/-1.7 mmol/L in control group (p<0.001) compared to 6.8+/-4.6 mmol/L for IgG MM and 8.4+/-4.37 mmol/L for IgA MM patients. Multiple myeloma patients stratified by clinical stages had anion gap of 8.7+/-1.7 in stage I, 7.93+/-0.47 in stage II and 5.65+/-0.31 in stage III. A significant correlation was found in IgG myeloma when anion gap was expressed as a function of the serum monoclonal protein concentration.
  
  
  CONCLUSIONS
  The anion gap is significantly lower in multiple myeloma patients compared to controls. Lowered anion gap is more specific feature of the IgG type MM. We suggest that correlation of AG with the disease severity and with paraproteins concentration could potentially be useful in monitoring patients for disease progression. However, longitudinal studies are required to confirm the utility of anion gap in monitoring patients with MM.
authors.affiliation: Department of Pathology and Microbiology, The Aga Khan University and Hospital, P.O. Box 3500, Karachi 74800, Pakistan. shireen.mansoor@aku.edu
authors.forename: Shireen
authors.initials: S
authors.lastname: Mansoor
authors.forename: Imran
authors.initials: I
authors.lastname: Siddiqui
authors.forename: Salman
authors.initials: S
authors.lastname: Adil
authors.forename: Ghulam
authors.initials: G
authors.lastname: Nabi Kakepoto
authors.forename: Zafar
authors.initials: Z
authors.lastname: Fatmi
authors.forename: Farooq
authors.initials: F
authors.lastname: Ghani
mesh_terms: D000136:Acid-Base Equilibrium; D000368:Aged; D000912:Antibodies, Neoplasm / Q000097:blood; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000175:diagnosis* / Q000473:pathology; D009367:Neoplasm Staging; D011379:Prognosis; D012720:Severity of Illness Index
chemical_list: D000912:Antibodies, Neoplasm; D007074:Immunoglobulin G