A prospective observational study of individuals with type 1 diabetes found that HbA1c levels were about 0.8% higher in blacks than in whites, but that based on the mean glucose level mean HbA1c should have been only about 0.4% higher. The findings demonstrate that HbA1c levels consistently overestimate the mean glucose level in black persons compared with white individuals, according to the authors (Ann Intern Med 2017; doi:10.7326/M16-2596).

The study involved 208 patients followed for 12 weeks at 10 U.S.-based diabetes centers. Participants were at least 8 years old, had had type 1 diabetes at least 2 years and had HbA1c levels 6.0%-12.0% within 3 months of enrollment.

The mean HbA1c level and continuous glucose monitoring glucose concentration in blacks were 9.1% and 191 mg/dL, respectively, compared with 8.3% and 180 mg/dL in whites. In contrast, while glycated albumin and fructosamine were highly correlated with HbA1c, the researchers did not observe statistically significant differences between these analytes and mean glucose concentration.

An accompanying editorial lauded the well-designed and carefully conducted study” but cautioned about generalizing its results. We should seek to better understand subgroups that may be prone to discordant HbA1c and glucose measures; such groups may overlap with race, but we should not conflate such conditions with race itself.”