Laboratory Methods for the Detection of Hemoglobinopathies in the Community Hospital

Abnormal haemoglobins, Hb Takamatsu and Hb G-Szuhu, detected during the analysis of glycated haemoglobin (HbA1C) by high performance liquid chromatography

BACKGROUND

During medical checkups of two unrelated female outpatients during their annual health examination and one male inpatient suffering from cardiac failure the glycated haemoglobin (HbA1C) concentrations measured by high performance liquid chromatography (HPLC) were low, in spite of normal fasting plasma glucose concentrations. However, HbA1C concentrations measured by latex immunoagglutination and fructosamine concentrations were within the normal range.

METHOD

Investigations were performed to elucidate the reasons for these discrepancies.

RESULTS

Abnormal haemoglobins, Hb Takamatsu and Hb G-Szuhu, were found. The HPLC chromatogram showed an additional peak near HbA1a + b, which resulted in falsely low HbA1C concentrations. Isoelectric focusing analysis of the patients' haemoglobin disclosed abnormal haemoglobins, which migrated faster than normal HbA1 in the two female patients and slower in the male patient. The cDNA sequence and amino acid analyses of the haemoglobin alpha-chains and beta-chains indicated the presence of the haemoglobin variant beta 120 Lys-->Gln in the two female patients and beta 80 Asn-->Lys in the male patient; that is, Hb Takamatsu and Hb G-Szuhu.

CONCLUSIONS

These cases show how these silent haemoglobin variants can result in falsely low HbA1C concentration readings when using HPLC.

Hemoglobin variants recently detected in Austria

Measurement of glycated hemoglobin (HbAtc) is used for routine management of diabetic patients. Glucose linkage to HbAtc reflects mean blood glucose levels during the last 3 months before examination. Various methods for HbA1c determination show abnormal values with hemoglobin variants. In some diabetic patients excessively high HbA1c values with high-performance liquid chromatography (HPLC) led to the detection of Hb Graz. In addition to Hb Graz, other silent hemoglobin variants have been found in Austria. Here we review Hb Graz, Hb Sherwood Forest, and Hb Okayama detected while using HPLC for the measurement of HbA1c in diabetic patients.