Prevalence of monoclonal gammopathy of undetermined significance in a large population with annual medical check-ups in China
Authors: Jian-hua Han, Ji-nuo Wang, Yue-lun Zhang, Xin-xin Cao, Dao-bin Zhou, Teng-da Xu, Wei Su, Jian Li
Journal: Blood Cancer Journal (2020)

Dear Editor,Monoclonal gammopathy of undetermined significance (MGUS) is a clinically asymptomatic premalignant plasma cell disorder, which may develop to multiple myeloma (MM), light-chain amyloidosis, Waldenstrom macroglobulinemia, or other related malignancies 1 .The crude prevalence of MGUS varies from 0.05% to 6.1% among distinct population from different countries, which is influenced by race, age, sex, family history, immunosuppression, and pesticide exposure 2 .So far, many population-based studies of MGUS come from the white or black population living in Western and African countries.One of the largest population-based study in the USA showed that the prevalence of MGUS was 3.2% in the Caucasian general population aged ≥50 years 3 , while the rate was even higher in African-Americans to be 3.7% 4 .However, data on the epidemiology of MGUS remain largely undefined in Asians.Some populationbased studies among population from Thailand, Korea, and Hong Kong were relatively limited due to small sample sizes [5][6][7] .Therefore, we conducted this study to determine the prevalence and characteristics of MGUS among a large population with annual medical check-ups in a well-defined geographic area in China.From December 2013 to April 2019, a total of 316,616 people received annual medical check-ups at the Peking Union Medical College Hospital.Generally, people who received annual medical check-ups at our institute were apparently healthy and reflected a population with relatively high social economic status and health consciousness in Beijing, China.All the people with measurement of serum protein electrophoresis were included in our analysis.People were excluded if age or sex was missing in the record.The information collected at the first time when the person came to our institute was regarded as baseline data, while consecutive follow-up records of the same participant were also collected (Supplementary Fig. 1).This study was approved by the institutional ethics committee of Peking Union Medical College Hospital and informed consent was waived because there is no information that can help to identify individuals.MGUS was defined in accordance with previous definition by International Myeloma Working Group 8 .Serum M protein was detected by capillary electrophoresis (Sebia, Parc Technologique Leonard de Vinci, Cedex, France).Patients with a positive or suspicious M protein were suggested to be referred to the hematological clinic for further assessment, including serum and/or urine immunofixation electrophoresis (IFE) to determine the type of immunoglobulin and serum free light chain (FLC) assays for quantification.Serum IFE was performed using the SPIFE ® ImmunoFix-9 Kit (Helena Laboratories, TX, USA).Urine IFE was detected by the HYDRAGEL 9 IF Kit (Sebia, Parc Technologique Leonard de Vinci, Cedex, France).FLC measurements were performed by an IMMAGE 800 automated nephelometer (Beckman Coulter, CA, USA) using commercially available kits (Hevylite ® , The Binding Site Ltd, Birmingham, UK).Published reference ranges for κ and λ FLC were used (3.3-19.4 and 5.7-26.3mg/L, respectively).An abnormal κ/λ FLC ratio was defined as <0.26 or >1.65 9 .Serum