HbA1c May Underestimate Glycemic Control in Blacks With Sickle Cell Trait

HealthDay News – Hemoglobin A1c (HbA1c) measurements may be less accurate in black people who have sickle cell trait (SCT), according to a study published online Feb. 7 in the Journal of the American Medical Association.

The research included 4,620 patients (average age, 52.3) — 1,572 from the CARDIA study, and 3,048 from the Jackson Heart Study. Both groups were evaluated to determine the association between SCT and HbA1c for given levels of fasting or two-hour glucose levels.

When assessing only HbA1c, the researchers found that 29.2% of blacks with SCT were diagnosed with prediabetes versus 48.6% of blacks without SCT. The corresponding numbers for diabetes were 3.8% and 7.3%. 

In unadjusted generalized estimating equations analyses, for a given fasting glucose, HbA1c values were lower in those with versus those without SCT (5.72% and 6.01%, respectively).

“Findings were similar in models adjusted for key risk factors and in analyses using 2001 concurrent measures of 2-hour glucose and HbA1c concentration for those with SCT (mean, 5.35%) vs those without SCT (mean, 5.65%) for a mean HbA1cdifference of −0.30% (95% CI, −0.39% to −0.21%)”.

“These findings suggest that HbA1c may systematically underestimate past glycemia in black patients with SCT and may require further evaluation,” the authors conclude.

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Lacy ME, Wellenius GA, Summer AE, et al. Association of sickle cell trait with hemoglobin A1cin African Americans. JAMA. 2017;317(5):507-515. doi:10.1001/jama.2016.21035