title: The effect of anaemia and abnormalities of erythrocyte indices on HbA1c analysis: a systematic review.
abstract: OBJECTIVE
  The use of HbA1c for the diagnosis of diabetes is now widely advocated despite caveats to its use. Anaemia is cited as a major confounder to this use; however, the effect of erythrocyte indices and to what degree anaemia influences HbA1c levels is not known.
  
  
  METHODS
  A systematic electronic database search of MEDLINE, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL) and the Cochrane Library was conducted for relevant articles published between January 1990 and May 2014. Included studies had at least one measurement of HbA1c and glucose, and a least one index of haematinic deficiency, involving non-pregnant adults, not known to have diabetes.
  
  
  RESULTS
  A total of 12 articles from 544 were included. The majority of studies focused on iron deficiency anaemia (IDA) and, in general, demonstrated that the presence of iron deficiency with or without anaemia led to an increase in HbA1c values compared with controls, with no concomitant rise in glucose indices. Data on the effects of other indices of erythrocyte abnormalities on HbA1c are limited but show a possible decrease in HbA1c values with non-iron deficiency forms of anaemia.
  
  
  CONCLUSIONS
  HbA1c is likely to be affected by iron deficiency and IDA with a spurious increase in HbA1c values; conversely, non-IDA may lead to a decreased HbA1c value. This may lead to confusion when diagnosing diabetes using HbA1c. This review clearly identifies the need for more evidence, especially in identifying the types and degrees of anaemia likely to have significant impact on the reliability of HbA1c.
authors.affiliation: School of Medicine, University of Nottingham, Derby, DE22 3DT, UK, emma.english@nottingham.ac.uk.
authors.forename: Emma
authors.initials: E
authors.lastname: English
authors.forename: Iskandar
authors.initials: I
authors.lastname: Idris
authors.forename: Georgina
authors.initials: G
authors.lastname: Smith
authors.forename: Ketan
authors.initials: K
authors.lastname: Dhatariya
authors.forename: Eric S
authors.initials: ES
authors.lastname: Kilpatrick
authors.forename: W Garry
authors.initials: WG
authors.lastname: John
mesh_terms: D000328:Adult; D000740:Anemia / Q000097:blood*; D018798:Anemia, Iron-Deficiency / Q000097:blood; D001786:Blood Glucose / Q000032:analysis; D003920:Diabetes Mellitus / Q000097:blood / Q000175:diagnosis; D004909:Erythrocyte Indices; D004912:Erythrocytes / Q000502:physiology*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D011247:Pregnancy; D015203:Reproducibility of Results
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin