title: Proportion of individuals with low serum vitamin B-12 concentrations without macrocytosis is higher in the post folic acid fortification period than in the pre folic acid fortification period.
abstract: BACKGROUND
  Large intakes of folic acid may delay the diagnosis of vitamin B-12 deficiency, which could lead to irreversible neuropathy.
  
  
  OBJECTIVE
  The objective of this study was to determine whether the proportion of individuals with low serum vitamin B-12 without macrocytosis (undiagnosed vitamin B-12 deficiency) has increased in the post-folic acid fortification period.
  
  
  METHODS
  Individuals aged >or=19 y with low serum vitamin B-12 (<258 pmol/L) and mean corpuscular volume (MCV) measured between 1995 and 2004 were identified from medical records. The proportion and odds ratios of individuals with low serum vitamin B-12 without macrocytosis by sex, race, and age according to prefortification (n = 86), perifortification (n = 138), and postfortification (n = 409) periods were determined.
  
  
  RESULTS
  MCV was significantly lower in the postfortification period (88.6 fL) than in the prefortification (94.4 fL; P < 0.001) and perifortification (90.6 fL; P = 0.007) periods. The proportion of subjects with low serum vitamin B-12 without macrocytosis was significantly higher in the postfortification (approximately 87%) and perifortification (approximately 85%) periods than in the prefortification period (approximately 70%; P < 0.001). In a sex-, race-, and age-adjusted analysis, the odds ratio for having low serum vitamin B-12 without macrocytosis was 3.0 (95% CI: 1.7, 5.2) in the postfortification period relative to the prefortification period.
  
  
  CONCLUSIONS
  Subjects with low serum vitamin B-12 were likely to be without macrocytosis in the postfortification period. MCV should not be used as a marker for vitamin B-12 insufficiency. It is possible that folic acid fortification may have led to a correction of macrocytosis associated with vitamin B-12 insufficiency.
authors.affiliation: Rush University Medical Center, Chicago, IL, USA.
authors.forename: Kelly F
authors.initials: KF
authors.lastname: Wyckoff
authors.forename: Vijay
authors.initials: V
authors.lastname: Ganji
mesh_terms: D000367:Age Factors; D000368:Aged; D000748:Anemia, Macrocytic / Q000175:diagnosis / Q000453:epidemiology; D016001:Confidence Intervals; D003937:Diagnosis, Differential; D004909:Erythrocyte Indices; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000009:adverse effects / Q000378:metabolism; D005527:Food, Fortified; D006801:Humans; D008297:Male; D008875:Middle Aged; D009752:Nutritional Status; D016017:Odds Ratio; D012737:Sex Factors; D014805:Vitamin B 12 / Q000097:blood* / Q000378:metabolism; D014806:Vitamin B 12 Deficiency / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology*; D014803:Vitamin B Complex / Q000008:administration & dosage* / Q000097:blood*
chemical_list: D014803:Vitamin B Complex; D005492:Folic Acid; D014805:Vitamin B 12