Interference of Hb J-Sardegna on HbA1c Quantification in a Diabetic Patient

BACKGROUND: Hb J-Sardegna represents a rare hemoglobin (Hb) variant with no previously documented interference in HbA1c quantification. In this study, we report the first case of Hb J-Sardegna incidentally identified in a diabetic patient, demonstrating significant discordance between measured blood glucose levels and disproportionately elevated HbA1c values. METHODS: The patient presented to our institution for follow-up evaluation of thyroid nodules, during which diabetes screening was clinically indicated. Plasma glucose levels were measured using biochemical analyzers, while HbA1c quantification was performed by high-performance liquid chromatography (HPLC). Hb fractions analysis was conducted by capillary electrophoresis (CE), with subsequent confirmation of the suspected variant through Sanger sequencing. RESULTS: Laboratory investigations revealed markedly elevated glucose levels (fasting: 8.79 mmol/L; 2-hour postprandial: 18.09 mmol/L), while HPLC analysis demonstrated a discordantly elevated HbA1c of 32.23%. CE identified an abnormal Hb fraction (Hb J peak: 31.8%), with subsequent Sanger sequencing confirming the presence of Hb J-Sardegna (HBA2:c.151C>G) and the intronic variant IVS-II-89T>C (HBA1:c.301-61T>C). Notably, all hematological parameters remained within normal ranges. CONCLUSIONS: This study reports for the first time that Hb J-Sardegna can interfere with HbA1c quantification, highlighting the importance for laboratory technicians to carefully interpret chromatographic profiles when analyzing HbA1c results.