A Case of Hb Quong Sze Co-Inherited Thai Deletion Resulting in Falsely Elevated HbA1c Values

Hb Quong Sze (Hb QS) is a rare Hb variant that, when combined with α0-thalassemia, can produce Hb QS-H disease. Reports of Hb QS-H disease affecting HbA1c testing are limited.

This study reports a case of Hb QS-H disease with abnormally elevated HbA1c levels measured by the G11 high-performance liquid chromatography (HPLC) system. Three additional detection systems (D100, Capillary Electrophoresis [CE], and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry [MALDI-TOF-MS]) were employed for comparative assessment of HbA1c values. Hemoglobin analysis was performed using CE, while conventional thalassemia gene detection utilized Gap-PCR and PCR-reverse dot blot (RDB).

The patient exhibited normal blood glucose levels (fasting: 4.18 mmol/L; 2-hour postprandial: 5.96 mmol/L), yet the G11 system recorded a markedly elevated HbA1c value of 18.4%. Among the three alternative detection systems, the D100 system yielded a value of 2.38%, while both CE and MALDI-TOF-MS failed to provide valid HbA1c measurements. Genetic analysis confirmed co-inheritance of Hb QS and Thai deletion in this patient.

Our findings demonstrate that Hb QS-H disease significantly interferes with HbA1c quantification, with methodological variability observed across different detection platforms.