title: Prevalence of monoclonal B-cell lymphocytosis: a systematic review.
abstract: BACKGROUND
  Individuals with monoclonal B-cell lymphocytosis (MBL) have been identified in clinic outpatients, in unaffected relatives of patients with chronic lymphocytic leukemia (CLL), and in general populations. MBL and its relationship with CLL have been actively investigated over the last decade. This report systematically reviews the prevalence of MBL in the context of the populations studied and the evolution of laboratory methods used to define MBL.
  
  
  METHODS
  To identify published studies that have assessed the prevalence of MBL, we systematically searched the MEDLINE databases and consulted with members of the International MBL Study Group. We reviewed the 10 articles that were identified by this process. We abstracted information on study populations, laboratory tests, criteria for designating MBL, and the reported frequencies.
  
  
  RESULTS
  Three of the ten studies were published in 2009, three between 2007 and 2008, and four between 2002 and 2004. Reported prevalences varied widely, ranging from 0.12 to 18.2%. This variability was clearly associated with both the laboratory methods and the populations studied. MBL was more common among older individuals and kindred of persons with CLL. The most common MBL subtype was CLL-like MBL.
  
  
  CONCLUSIONS
  Large population-based studies of MBL that employ standardized laboratory methods with a consensus case definition are needed to assess prevalence and establish risk factors. These studies should include prospective follow-up of MBL cases to determine the relationship between MBL and CLL. Data from original studies should be reported in sufficient detail to allow future synthesis of information from multiple studies, such as meta-analysis.
authors.affiliation: Division of Health Studies, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia, USA. yshim@cdc.gov
authors.forename: Youn K
authors.initials: YK
authors.lastname: Shim
authors.forename: Dannie C
authors.initials: DC
authors.lastname: Middleton
authors.forename: Neil E
authors.initials: NE
authors.lastname: Caporaso
authors.forename: Jane M
authors.initials: JM
authors.lastname: Rachel
authors.forename: Ola
authors.initials: O
authors.lastname: Landgren
authors.forename: Fatima
authors.initials: F
authors.lastname: Abbasi
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Raveche
authors.forename: Andy C
authors.initials: AC
authors.lastname: Rawstron
authors.forename: Alberto
authors.initials: A
authors.lastname: Orfao
authors.forename: Gerald E
authors.initials: GE
authors.lastname: Marti
authors.forename: Robert F
authors.initials: RF
authors.lastname: Vogt
mesh_terms: D001402:B-Lymphocytes / Q000473:pathology*; D002999:Clone Cells; D005260:Female; D014943:Global Health; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000276:immunology / Q000473:pathology; D018655:Lymphocyte Count; D008218:Lymphocytosis / Q000453:epidemiology* / Q000276:immunology / Q000473:pathology; D016239:MEDLINE; D008297:Male; D015995:Prevalence