HbA1c provides a broader perspective of a patient’s glycemic control compared to the snapshot granted by blood glucose measurement. However, instances exist in which the utility of HbA1c diminishes in diabetic monitoring. We present the 8th case report in which dapsone interfered with the ability of HbA1c to accurately depict the glycemic status of a patient.
Methods : We compared how HbA1c levels, blood glucose levels, Hb, and total bilirubin levels changed throughout the patient's life since 2010 and while the patient was on dapsone therapy vs off the therapy.
The patient is a diabetic Caucasian male who was 76 when started on dapsone on December 9th, 2013 for lichen planus. The patient’s HbA1c values ranged from 7.2-8.9% during the four years before therapy. Two months after dapsone was started, HbA1c dropped to 6.9% and remained at 4.8%-5.8% until the drug was discontinued on May 11th, 2016. Three months later, HbA1c levels increased to 7.6% and ranged from 7.3%-7.8% until June the following year. The average HbA1c while off dapsone was 7.6% compared to 5.58% while on dapsone. In addition, fingerstick glucose values while on dapsone vs off did not differ significantly. Fingerstick glucose levels consistently suggested poor glycemic control since 2010.
Because HbA1c levels decreased in the presence of elevated fingerstick glucose, fructosamine levels were analyzed. Fructosamine refers to proteins that are nonenzymatically glycated via ketoamine linkages at the N-amino terminal (Danese et al 2015). Because albumin is the major serum protein, fructosamine primarily reflects glycated albumin. As opposed to erythrocytes, albumin exists in the blood for about two weeks. Therefore, fructosamine, indicates recent glycemic status for a narrower window than HbA1c. On July 23rd, 2015 the patient’s fructosamine levels were 299 mcmol/L (reference range: 200-285 mcmol/L) while HbA1c was 4.9%. As a result, the fructosamine results indicate that the glycemic control had not improved as suggested by the HbA1c values.
Discussion : A side effect of dapsone is hemolytic anemia. While on dapsone, the patient's average Hb level dropped from 14.3 g/dL to 12.9 g/dL. Simultaneously, average total bilirubin levels increased from 0.43 mg/dL to 0.83 mg/dL, suggesting a hemolytic anemia. We propose that this dapsone-generated hemolytic anemia reduced erythrocyte exposure to glucose, thus decreasing HbA1c values. As a result, HbA1c was unreliable in monitoring his glycemic control during this time.
Conclusion : Clinicians should be wary when monitoring the course of diabetic disease in patients on dapsone therapy and consider alternative methods of diabetic monitoring, such as fructosamine.
University of Illinois College of Medicine, US Navy
Third year Navy HPSP medical student.