title: Vitamin B12 deficiency--need for a new guideline.
abstract: OBJECTIVE
  Many patients with vitamin B12 deficiency do not have anemia or macrocytosis, but the prevalence of B12 deficiency in patients without macrocytosis is not known.
  
  
  METHODS
  We investigated the prevalence of B12 deficiency among patients with normocytosis and microcytosis and recommended a screening strategy. All patients (n = 3714) with serum B12 measured at the Prince of Wales Hospital in 1996 were reviewed. The prevalence of serum B12 less than 140 pmol/L was determined for the following patient subgroups: younger than 70 y, older than 70 y, anemic, non-anemic, macrocytic, normocytic, microcytic, documented iron deficiency, and documented thalassemia.
  
  
  RESULTS
  The prevalence of B12 deficiency (<140 pmol/L) ranged from 4.8% to 9.8% among the different subgroups.
  
  
  CONCLUSIONS
  Whatever screening criteria were used, a significant number of B12-deficient patients will be missed. Therefore, there may be a case for universal vitamin B12 screening.
authors.affiliation: Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: C H
authors.initials: CH
authors.lastname: Chui
authors.forename: F Y
authors.initials: FY
authors.lastname: Lau
authors.forename: R
authors.initials: R
authors.lastname: Wong
authors.forename: O Y
authors.initials: OY
authors.lastname: Soo
authors.forename: C K
authors.initials: CK
authors.lastname: Lam
authors.forename: P W
authors.initials: PW
authors.lastname: Lee
authors.forename: H K
authors.initials: HK
authors.lastname: Leung
authors.forename: C K
authors.initials: CK
authors.lastname: So
authors.forename: W C
authors.initials: WC
authors.lastname: Tsoi
authors.forename: N
authors.initials: N
authors.lastname: Tang
authors.forename: W K
authors.initials: WK
authors.lastname: Lam
authors.forename: G
authors.initials: G
authors.lastname: Cheng
mesh_terms: D000367:Age Factors; D000368:Aged; D000740:Anemia / Q000453:epidemiology; D000748:Anemia, Macrocytic / Q000453:epidemiology; D000752:Anemia, Pernicious / Q000453:epidemiology; D001772:Blood Cell Count; D002681:China / Q000453:epidemiology; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008297:Male; D008403:Mass Screening; D015995:Prevalence; D012189:Retrospective Studies; D014805:Vitamin B 12 / Q000097:blood*; D014806:Vitamin B 12 Deficiency / Q000453:epidemiology*
chemical_list: D014805:Vitamin B 12