A lab recently implemented a new HbA1c electrophoresis assay, and one of the flags that has popped up more than others is a broad peak of A1c. What does this finding mean? Respondents say possible causes could include an interfering hemoglobin fragment, a rare post-translational modification, or a low-abundance, perhaps unstable hemoglobin gene product. Those who have experienced the same thing do not report the A1c value. Instead, they either send to a reference lab that uses another method or perform a CBC to check for a hemoglobinopathy.