Discordantly Low Hemoglobin A1c in the Context of Marked Hyperglycemia: A Case Report Implicating Elevated Fetal Hemoglobin (4.1%)
Mustafa Ibrahim Abbas; Mubarak Ahmed Elshafia; Khalid Abdelsamea Mohamedahmed; Yousif Abdelhameed Mohammed; Sarah Hameed Aldhafiri; Fayhaa Mahmood Madani Hamood; Mazza Alsayed Adam; Omar Osman Mohamed; Ahmed Mohamed Ahmed
Abstract
Hemoglobin A1c (HbA1c) is main biomarker for assessing long-term hypo and hyperglycemic management. However, depending on the technique, elevated levels of fetal hemoglobin (HbF) can impact the precision of HbA1c tests, potentially producing deceptively low HbA1c values even in cases of significant hyperglycemia. An outpatient evaluated on 2025-06-16 had highly positive urine ketones (+++) and significant hyperglycemia (random blood glucose: 433 mg/dL), which are consistent with a diagnosis of diabetic ketoacidosis. Paradoxically, the HbA1c measured by conventional immunoassay was 6.5%, falling into the non-diabetic category. An elevated fetal hemoglobin (HbF) concentration of 4.1% was revealed by follow-up hemoglobin fractionation, raising concerns about assay interference and prompting a reevaluation of the HbA1c result. Elevated HbF hemoglobin of greater than 4% can mistakenly reduce HbA1c, particularly when employing immunoassay or boronate-affinity methods. To precisely guide management, clinicians should incorporate other glycemic indicators or continuous glucose monitoring, and ionexchange HPLC or electrophoresis is advised.