HEMOGLOBIN-O PADOVA AND FALSELY LOW HEMOGLOBIN A(1C) IN A PATIENT WITH TYPE-I DIABETES

Glycated haemoglobin (HbA(1c)) measured by high performance Liquid chr omatography (HPLC) in a 20 year old female with insulin dependent diab etes mellitus was consistently within the normal range although her da ily blood glucose values were > 11.1 mmol/l. HbA(1c) measured by immun oagglutination and fructosamine was elevated and correlated with the p atient's blood glucose values. The HPLC chromatogram showed an additio nal peak at HbA(o). Electrophoresis of haemoglobin on citrate agar gel revealed an abnormal haemoglobin anodal of HbS. Cellulose acetate ele ctrophoresis and isoelectric focusing demonstrated an additional haemo globin migrating close to HbA(2). Amino acid analysis and DNA sequenci ng revealed an alpha 30 (B11) Glu --> Lys replacement, that is, haemog lobin O Padova. Investigations of two family members without diabetes revealed the same rare haemoglobin variant. This case showed that this silent haemoglobin mutation caused an additional peak and falsely low HbA(1c) values when measured by HPLC, the gold standard for this eval uation.