Glycated hemoglobin (HbA1c) is used for the assessment of glycemic control in patients with diabetes. The presence of genetic variants of hemoglobin can profoundly affect the accuracy of HbA1c measurement. Here, we report two cases of Hemoglobin G-Coushatta (HBB:c.68A>C) variant that interferes in the measurement of HbA1c by a cation-exchange HPLC (CE-HPLC) method. HbA1c was measured by a CE-HPLC method in a Tosoh HLC-723 G7 instrument. The HbA1c levels were 2.9% and 4%. These results alerted us to a possible presence of hemoglobinopathy. In the hemoglobin variant analysis, HbA2 levels were detected as 78.3% and 40.7% by HPLC using the short program for the Biorad Variant II. HbA1c levels were measured by an immunoturbidimetric assay in a Siemens Dimension instrument. HbA1c levels were reported as 5.5% and 5.3%. DNA mutation analysis was performed to detect the abnormal hemoglobin variant. Presence of Hemoglobin G-Coushatta variant was detected in the patients. The Hb G-Coushatta variants have an impact on the determination of glycated hemoglobin levels using CEHPLC resulting in a false low value. Therefore, it is necessary to use another measurement method.
Glikolizirani hemoglobin (HbA1c) koristi se za procenu glikemijske kontrole kod obolelih od dijabetesa. Prisustvo genetskih varijanti hemoglobina može snažno uticati na tačnost merenja HbA1c. Ovde je prikazan izveštaj o dva slučaja gde je varijanta hemoglobina G-Coushatta (HBB:c.68A>C) uticala na merenje HbA1c metodom HPLC sa katjonskom izmenom (CE-HPLC). HbA1c meren je metodom CE-HPLC na instrumentu Tosoh HLC-723 G7. Nivoi HbA1c bili su 2,9% i 4%. Ovi rezultati ukazali su nam na potencijalno prisustvo hemoglobinopatije. Prilikom analiziranja varijante hemoglobina, otkriveni su nivoi HbA2 od 78,3% i 40,7% metodom HPLC uz korišćenje kratkog programa za Biorad Variant II. Nivoi HbA1c mereni su pomoću imunoturbidimetrijskog eseja na instrumentu Siemens Dimension. Dobijeni su nivoi HbA1c od 5,5% i 5,3%. Analiza mutacije DNK izvedena je kako bi se otkrile abnormalne varijante hemoglobina. Kod pacijenata je otkriveno prisustvo varijante hemoglobina G-Coushatta. Varijante Hb G-Coushatta utiču na određivanje nivoa glikoliziranog hemoglobina pomoću metode CE-HPLC, {to ima za posledicu lažno niske vrednosti. Dakle, neophodno je primeniti druge metode merenja.
Keywords: Hb G-Coushatta (HBB:c.68A>C); HbA1c; cation-exchange HPLC.