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Document Details : Title: Spuriously high HbA1c due to the presence of haemoglobin Raleigh: a case report and review of the literature Author(s): VANDEWIELE A, GENBRUGGE K, DELANGHE J Journal: Acta Clinica Belgica Volume: 65 Issue: 5 Date: 2010 Pages: 336-340 DOI: 10.2143/ACB.65.5.1002434 Abstract : Case summary 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 μmol/l (ref. range 205-285 μmol/l)). Genetic testing lead to the identification of an uncommon and clinically silent haemoglobin variant, designated Raleigh, in which a mutation of the β chain results in the replacement of the N-terminal valine by acetylated alanine. Discussion 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). Conclusion 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. |
