Prevalence of monoclonal gammopathy of undetermined significance in Eswatini: a population-based study in Africa.

Abstract

Although monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma disproportionately affect Black individuals, few epidemiological studies have been conducted on these plasma cell disorders in Africa. Here we describe the prevalence of MGUS in Eswatini and compare our results to the landmark Olmsted County, Minnesota study. Between 2016 and 2017, 13 339 residents of Eswatini participated in the Swaziland HIV Incidence Measurement Survey, from which a nationally representative biorepository was created. Plasma samples were then randomly selected and analyzed for MGUS. MGUS prevalence in Eswatini was compared with that of Olmsted County. In addition, demographic and HIV-related associations with MGUS were assessed. Of the 515 samples randomly selected, the median age was 50 years (range = 35-80 years); 60% were female; and 38.6% were HIV positive, of whom 82.4% were on antiretroviral therapy. We found that 68 participants had evidence of MGUS, for a prevalence of 13.2%. HIV status was not significantly associated with MGUS (odds ratio = 1.05, 95% confidence interval = 0.62 to 1.77), but among HIV-positive individuals, MGUS was less frequent for patients on antiretroviral therapy (adjusted odds ratio = 0.31, 95% confidence interval = 0.11 to 0.82). The prevalence of conventional MGUS was similar between Eswatini and Olmsted County (3.4% vs 3.2%-3.4%), whereas the incidence of light-chain MGUS was significantly greater in Eswatini (12.3% vs 0.8%). Our study suggests that the incidence of MGUS is similar between ethnicities and raises the question of whether the current definition of light-chain MGUS reliably reflects a true monoclonal protein precursor state. Perhaps the current definition of light-chain MGUS may be capturing alternate etiologies, such as untreated HIV infection.