The incidence of multiple myeloma (MM) is markedly higher in blacks compared with whites. This may be related to a higher prevalence of monoclonal gammopathy of undetermined significance (MGUS), the premalignant lesion that precedes MM. Our objective was to define the prevalence and risk factors of MGUS in blacks, Hispanics, and whites using a large cohort representative of the United States (U.S.) population.
Of 13,278 adults age ≥50 years enrolled in National Health and Nutritional Examination Survey (NHANES) III or NHANES 1999–2004, stored serum samples to test for monoclonal proteins were available on 12,482 persons (2,331 non-Hispanic blacks considered “black”, 2,475 Hispanics, 7,051 non-Hispanic whites considered “white”, and 625 “others”). Agarose-gel electrophoresis, serum protein immunofixation, serum free light-chain assay, and typing of the M-protein was performed on sera from all subjects. Unadjusted and adjusted prevalence rates were computed from logistic regression analysis. Risk factors were studied using available survey information available from NHANES. Main outcomes and measures were prevalence of MGUS by age, gender, race, ethnicity, and risk factors from available survey information.
MGUS was identified in 365 participants, for an overall prevalence of 2.4%. Adjusted prevalence of MGUS was significantly higher (p<0.001) in blacks (3.7%) compared with whites (2.3%) (p=0.001) or Hispanics (1.8%). MGUS in blacks had characteristics that posed a greater risk of progression to MM. The prevalence of MGUS (adjusted for age, education, sex, race, smoking) was 3.1% and 2.1% for the North and Midwest versus South and West regions of the U.S., respectively (p=0.052).
MGUS is significantly more common in blacks, and more often has features associated with higher risk of progression to MM. We also find a strong geographic disparity in the prevalence of MGUS between the North/Midwest versus the South/West regions of the U.S., which has etiologic implications.