In using ion-exchange chromatographic methods, falsely increased levels of Hgb A1c might be demonstrated in the presence of:

• A. iron deficiency anemia
• B. pernicious anemia
• C. thalessemias
• D. Hgb S

Answer: (D)

The test is about how abnormal hemoglobins can interfere with HbA1c measurement when using ion-exchange chromatography. In this method, hemoglobins are separated by their charge, and the HbA1c fraction is identified based on subtle charge differences introduced by glycation. If a variant like HbS is present, it changes the charge and behavior of the hemoglobin during the chromatographic run, which can cause HbS-containing molecules to co-elute with the HbA1c fraction or create overlapping peaks. This overlap can make the instrument report a higher HbA1c than is truly present, producing a falsely elevated result.

Other conditions listed affect HbA1c more through biology (such as altered red cell lifespan) rather than by chromatographic interference in this assay, so they do not consistently cause the same spurious elevation in ion-exchange HbA1c measurements.