Delay in diagnosis of diabetes mellitus due to inaccurate use of hemoglobin A1C levels.

Testing of hemoglobin A(1C) (HbA(1C)) levels has become widespread in the management of patients with diabetes mellitus. Since the 1980s, it has proven to be an invaluable tool correlating with a patient's average blood glucose levels as well as with their disease morbidity. Clinicians often base treatment decisions and make adjustments depending on a patient's HbA(1C) level. As useful as the HbA(1C) is, it does have notable limitations. A number of conditions can lead to a falsely elevated or a falsely low HbA(1C) level. When one of these conditions is present, it is important to recognize the inaccuracy of the HbA(1C) test to prevent a delay or error in the diagnosis or care of patients with diabetes mellitus. It is also important to be aware of alternative methods of monitoring a patient's diabetes such as a fructosamine assay or home and office blood glucose measurements. Presented is the case of a patient with diabetes mellitus and hereditary spherocytosis, a condition that interfered with her HbA(1C) value and resulted in a delay in her care.