Hemoglobin (Hb) A1c levels appear to be higher in blacks than in whites regardless of glucose levels. This suggests that HbA1c screening could have limited usefulness in reflecting glucose intolerance, predicting the risk of diabetes complications, and measuring quality of care.

Although research has shown that in the presence of prediabetes, HbA1c levels are higher in blacks than in whites when there is no difference in glucose concentration, investigators sought to determine whether this held true across the full spectrum of glycemia.

In the study (Ann Intern Med. 2010;152:770-777), HbA1c levels were consistently higher in black than in white populations, glucose levels notwithstanding: For people with normal glucose tolerance, HbA1c was 0.13 of a percentage point higher for blacks in the 18+ age group and 0.21 of a percentage point higher for blacks in the over-40 group. For those with prediabetes, HbA1c was 0.26 and 0.3 of a percentage point higher in blacks in the 18+ and over-40 groups, respectively. In people who were shown to have diabetes, HbA1c was 0.47 of a percentage point higher for blacks in both study populations.

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Recent research has also shown that a morning urine test is best for detecting declining kidney performance in people with diabetic nephropathy. Investigators evaluated the effectiveness of four urinary measures in predicting renal events in 701 individuals with type 2 diabetes and nephropathy: urinary protein excretion and urinary albumin excretion from a 24-hour urine collection, and urinary albumin concentration and albumin:creatinine ratio from a first-morning void. The last proved to be the superior method, implying that collection of first-morning voids—more convenient than 24-hour urine collection—can be used to assess proteinuria. ( J Am Soc Nephrol. 2010;21:1243-1244).