Interference of abnormal hemoglobins on the measurement of hemoglobin A1c by ion-exchange chromatography

The number of unexpected HbA variants may be a greater problem in routine practice than is generally realized

BACKGROUND

The majority of variant and abnormal haemoglobins are clinically silent but may not be biochemically silent when it comes to HbA1c estimation.

CASE REPORT

We describe several cases in which there were problems in the determination of HbA1c for monitoring diabetes in patients that would not normally be classified as being at risk. Four of these cases were sufficiently unusual to warrant individual publication but all came from a very restricted geographical area with a population of only approximately 500,000. The significance of this is not that variant haemoglobins affect HbA1c analysis but that the occurrence of unexpected/unusual variant haemoglobins may be more frequent than most clinicians would expect, considering that only a small proportion of the basal population are diabetic and have their HbA1c monitored. Differences will exist between different areas due to differences in both the prevalence of variants and the analytical methods employed.

CONCLUSIONS

Consequently, we propose greater interaction between diabetologists and the laboratory in an attempt to identify these clinically but not biochemically silent variants to achieve a true estimation of the glycaemic control in affected patients.

Measuring glycated proteins: clinical and methodological aspects

The recognition that nonenzymatic glycation, wherein free sugar condenses with certain reactive protein amino groups, is increased in hyperglycemic states has led to improved means for assessing diabetic control through the measurement of concentrations of glycated proteins in the circulation. This article reviews the chemistry, methods for measurement, and clinical relevance of circulating glycated proteins in the management of diabetes.