Haemoglobin O Padova and falsely low haemoglobin A1c in a patient with type I diabetes

HbA mutation causing false-normal HbA1c results determined by HPLC in a patient with type 2 diabetes mellitus: A case report

Glycated hemoglobin A1c (HbA1c) is a convenient measure of long-term blood glucose concentrations and it is an accepted diagnostic test for type 2 diabetes mellitus (T2DM). The present study reported on a female patient with T2DM, whose fasting blood glucose and glycated albumin levels were elevated, while the HbA1c levels were in the normal range, which was inconsistent with the patient's clinical diagnosis. In the subsequent analysis, genomic DNA was extracted from the patient's blood and the HbA genes were analyzed by Sanger sequencing. The results indicated that the patient's HbA α1/2-chain genes had no mutations, while two HbA β-chain gene mutations were present, including an HBB:c.9T>C variant and a Hb G-Coushatta variant. The HBB:c.9T>C variant is a silent mutation that has no effect on HbA1c levels when detected by ion-exchange high-performance liquid chromatography (HPLC), while the Hb G-Coushatta variant may cause a discrepancy between blood glucose control and HbA1c levels when detected by ion-exchange HPLC. These results suggested that the Hb G-Coushatta variant gave rise to the false-normal result regarding HbA1c levels when detected by ion-exchange HPLC that was inconsistent with the clinical manifestations in this patient.

Factitious biochemical measurements resulting from hematologic conditions

Factitious laboratory results often lead to unnecessary testing or treatment. This brief review of factitious biochemical results due to preexisting hematologic conditions focuses on the mechanisms underlying the factitious results and suggests ways to prevent them. An observant pathologist identifies these errors, intervenes in a timely fashion, investigates the sources of error diligently, and institutes measures to prevent their recurrence.

Hemoglobin variant HbE found in two South Asian diabetic patients

Glycohemoglobin, also known as hemoglobin (Hb) A(1c), is a marker of long-term glycemic control in patients with diabetes. We present two South-Asian diabetic patients whose HbA(1c) peaks were not measurable using high performance liquid chromatography (HPLC). Further investigations showed that these patients were homozygous for a hemoglobin variant, HbE (beta26 Glu-->Lys). Because of the increasing numbers of immigrants in Japan, area-specific hemoglobinopathies are now encountered more frequently than before. Thus, if discrepant results are found on an HbA(1c) assay or if the HbA(1c) value cannot be measured, such patients should be screened for hemoglobinopathies and alternative measurements for monitoring diabetes should be considered.

Silent haemoglobin variants and determination of HbA(1c) with the HPLC Bio-Rad Variant II

AIMS

To evaluate the determination of HbA(1c) with an automated high performance liquid chromatography (HPLC) method in patients with clinically silent haemoglobin variants.

METHODS

HbA(1c) values were determined with the ion exchange HPL Bio-Rad Variant II using the high resolution beta thalassaemia programme in patients with silent haemoglobin variants, namely: Hb Graz, Hb Sherwood Forest, Hb O Padova, and Hb D.

RESULTS

All of these haemoglobin variants caused additional peaks in the chromatograms. No clinically useful HbA(1c) results were produced for patients with Hb Graz and Hb Sherwood Forest, the results for the patient with Hb D were too low, but the results for patients with Hb O Padova were acceptable.

CONCLUSIONS

The development of this automated HPLC method modification with high resolution mode aids the identification of interference caused by the described clinically silent haemoglobin variants in HbA(1c) determination.

Hemoglobin variants and determination of glycated hemoglobin (HbA1c)

Measurement of glycated hemoglobin in diabetic patients is an established procedure for evaluating long-term control of diabetes. The Diabetes Control and Complications Trial (DCCT), as well as the United Kingdom Prospective Diabetes Study (UKPDS), confirmed the direct relationship between the degree of glycemic control as estimated by glycohemoglobin (GHb) determinations and the development and progression of long-term complications in diabetic patients. Samples with known interferences of HbA(1c) determination as hemoglobinopathies are specifically excluded from certification testing and there are no guidelines or requirements for comparability of samples containing hemoglobin (Hb) variants. This paper reviews the interference of Hb variants on determination methods of glycated hemoglobin as they result in false HbA(1c) results.

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.