In Reply Mr Rohlfing and colleagues point out a limitation of our recent study, namely that HbA1c levels in participants in the Jackson Heart Study and the Coronary Artery Risk Development in Young Adults Study were only assessed using 2 versions of the Tosoh ion-exchange high-performance liquid chromatography assays. As noted in the article, our data did not permit us to distinguish whether the findings were due to assay interference by SCT or physiologic differences between participants with vs without SCT. Rohlfing and colleagues stipulate that the differences in HbA1c levels between participants with vs without SCT can be mostly or fully accounted for by analytic interference from SCT with these 2 assays.1 We agree that this is a plausible hypothesis that warrants further investigation. Another plausible hypothesis is that our findings are due, at least in part, to a biological difference in red blood cell lifespan in those with and without SCT. Although data are limited, the presence of HbS is thought to result in a shorter lifespan for red blood cells, which would result in less time available for hemoglobin glycation and hence lower HbA1c values.2,3 The available data do not allow us to distinguish whether our findings are attributable to biological differences between those with and without SCT or analytic interference by SCT with these particular HbA1c assays.
Lacy ME, Wellenius GA, Wu W. Measurement of Hemoglobin A1c in Patients With Sickle Cell Trait—Reply. JAMA. 2017;317(21):2237–2238. doi:10.1001/jama.2017.4646
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