Spuriously high HbA1c due to the presence of haemoglobin Raleigh: a case report and review of the literature.
METHODS
The described case concerns a Caucasian obese female patient who presented with a spuriously high haemoglobin A1c value of 45.6% (ref. range 4.0-6.1%), as measured with one of the three cation-exchange chromatography methods used. Re-evaluation of serum haemoglobin A1c and glycohaemoglobin with immunoassay and affinity binding chromatography resulted in normal levels (4.14% (ref. range 4.0-6.0%) and 4.3% (ref. range < 6%), respectively). In addition, the patient's serum fructosamine value--another indicator of plasma glucose concentration over time--was low (184 micromol/l (ref. range 205-285 micromol/l)). Genetic testing lead to the identification of an uncommon and clinically silent haemoglobin variant, designated Raleigh, in which a mutation of the chain results in the replacement of the N-terminal valine by acetylated alanine.


CONCLUSIONS
Some Hb variants give rise to analytical errors in the HbA1c determination (e.g. co-elution of haemoglobin Raleigh with HbA1c in cation-exchange chromatography), whereas other Hb variants are associated with a shorter RBC turnover or a different glycation rate, which causes interpretation problems (e.g. no glycation of the acetylated alanine in haemoglobin Raleigh).


CONCLUSIONS
This article illustrates the difficulties in diabetes management in patients with a haemoglobin variant and it provides the clinician with a diagnostic flow chart for dealing with suspicious haemoglobin A1c values.
Department of Clinical Chemistry, Ghent University Hospital, Ghent, Belgium.
A
A
Vandewiele
K
K
Genbrugge
J
J
Delanghe
D000328:Adult; D002623:Chemistry Techniques, Analytical; D002851:Chromatography, High Pressure Liquid; D003920:Diabetes Mellitus / Q000175:diagnosis; D003951:Diagnostic Errors; D005260:Female; D014644:Genetic Variation; D006442:Glycated Hemoglobin / Q000032:analysis*; D006455:Hemoglobins, Abnormal / Q000235:genetics*; D006801:Humans
D006442:Glycated Hemoglobin; D006455:Hemoglobins, Abnormal; C083887:hemoglobin Raleigh