RESUMEN
BACKGROUND: Glycated hemoglobin, measured as HbA1c is used as an index of mean glycemia in diabetic patients over the preceding 2-3 months. Various assay methods are used to measure HbA1c and many factors may interfere with its measurement according to assay method used, causing falsely high or low results. OBJECTIVE: To report a case of diabetic patient with clinically silent hemoglobin variant, causing undetectable HbA1c concentration using ion-exchange high performance liquid chromatography (HPLC) method. CASE SUMMARY: Our patient is a 65-year-old female with type 2 diabetes mellitus on diet control, hypertension and hypercholesterolemia. Her fasting blood glucose concentrations ranged from 6.2 to 7.8 mmol/L. Her HbA1c concentrations measured with immunoturbidimetry method (Cobas Integra, Roche Diagnostics) ranged from 6.11 to 7.23%, but were undetectable when measured with ion-exchange HPLC [Arkray HA8160, Diabetes Mode (also known as Menarini HA8160)]. Hemoglobin analysis identified the presence of a hemoglobin variant--Hemoglobin D Punjab. CONCLUSIONS: Clinical laboratories should be aware of limitations of the HbA1c assay method used, such as potential interference with hemoglobin variant as depicted by our case. Alternative methods for monitoring glycemic control in these patients should be considered.