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A Pitfall in HbA1c Testing Caused by Hb Long Island Hemoglobin Variant
Luo Wei1, Yao Nan2, Bian Ying3
1Clinical Laboratory Department, Tianjin Medical University General Hospital, Tianjin, China.
Laboratory Medicine
|June 2, 2019
Summary
Hemoglobin (Hb) variants can significantly interfere with HbA1c measurements. A routine check revealed an Hb variant, Hb Long Island, in a patient, leading to an unusual HbA1c value of 0.
Area of Science:
- Clinical Chemistry
- Genetics
- Hematology
Background:
- Hemoglobin (Hb) variants are critical factors that can interfere with accurate HbA1c measurements.
- Understanding these interferences is crucial for correct diabetes mellitus diagnosis and management.
Observation:
- A 32-year-old Manchu Chinese woman presented with an unexpectedly low HbA1c level of 0 during a routine health examination.
- Advanced testing methods, including HPLC, capillary electrophoresis, PCR, and sequencing, were employed to investigate the anomaly.
Findings:
- The patient was found to have Hb Long Island, a hemoglobin variant, identified through HbA1c analysis.
- Genetic analysis revealed transversion mutations in exon 1 of the beta gene (HBB:c.8A > C, 9T > C), causing a His to Pro amino acid substitution.
- These mutations directly led to a significant decrease in the measured HbA1c value.
Implications:
- This case highlights the importance of considering Hb variants when HbA1c results do not correlate with clinical presentation.
- Careful examination of HbA1c chromatograms is essential for detecting interfering variants.
- Accurate HbA1c measurement relies on recognizing and accounting for hemoglobinopathies.
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