title: Patterns of monoclonal immunoglobulins and serum free light chains are significantly different in black compared to white monoclonal gammopathy of undetermined significance (MGUS) patients.
abstract: Monoclonal gammopathy of undetermined significance (MGUS), the precursor to multiple myeloma, is more common in blacks than whites. The serum free light chain (sFLC) assay is an important prognostic test in MGUS, but no study has evaluated sFLC levels and ratios in black MGUS patients. One-hundred and twenty-five black MGUS patients at two urban centers were compared to the white population of the Mayo Clinic. The median age for blacks was 73 years [41-94] and 75% were male. The M-protein isotype in blacks was 81% IgG, 13% IgA, 2% IgM, and 4% biclonal compared to 70%, 12%, 16%, and 2%, respectively, in whites, (P < 0.0005). The median M-protein concentration for blacks was 0.44 gm/dL (trace-2.33) compared to 1.2 gm/dl in whites. An abnormal sFLC ratio was present in 45% of black compared to 33% of white (P = 0.01) patients. Using the Mayo Clinic risk model, black patients had a significantly lower proportion of higher risk MGUS compared to whites: low 43%, low-intermediate 45%, high-intermediate 10%, and high 2% (P = 0.014). Black patients with MGUS have significantly different laboratory findings compared to whites. The biologic basis for these disparities and their effect on prognostic assessment is unknown. Prognostic models based on these biomarkers should be used cautiously in nonwhite populations.
authors.affiliation: Hematology-Oncology, Brooke Army Medical Center, San Antonio, Texas, USA. brendan.weiss@us.army.mil
authors.forename: Brendan M
authors.initials: BM
authors.lastname: Weiss
authors.forename: Alex
authors.initials: A
authors.lastname: Minter
authors.forename: Jude
authors.initials: J
authors.lastname: Abadie
authors.forename: Robin
authors.initials: R
authors.lastname: Howard
authors.forename: Joao
authors.initials: J
authors.lastname: Ascencao
authors.forename: Geraldine P
authors.initials: GP
authors.lastname: Schechter
authors.forename: Michael
authors.initials: M
authors.lastname: Kuehl
authors.forename: Ola
authors.initials: O
authors.lastname: Landgren
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044383:Black People / Q000706:statistics & numerical data*; D019411:Clinical Laboratory Techniques; D005260:Female; D006801:Humans; D007132:Immunoglobulin Isotypes / Q000032:analysis*; D007147:Immunoglobulin Light Chains / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D008998:Monoclonal Gammopathy of Undetermined Significance / Q000175:diagnosis* / Q000208:ethnology*; D009194:Myeloma Proteins / Q000032:analysis; D011379:Prognosis; D044465:White People / Q000706:statistics & numerical data
chemical_list: D007132:Immunoglobulin Isotypes; D007147:Immunoglobulin Light Chains; D009194:Myeloma Proteins; C085016:multiple myeloma M-proteins