Alternative measures didn't help in conditions thought to affect accuracy of HbA1c level
Using fructosamine or glycated albumin did not improve overall accuracy of glycemic measurement in an African population overall or in patients with sickle cell trait, anemia, or renal impairment, according to a comparison of these measures with HbA1c level and continuous glucose monitoring.
Switching to fructosamine or glycated albumin measurement is unlikely to improve the accuracy of glycemic monitoring over HbA1c level in patients with conditions reported to affect HbA1c reliability, a study found.
To assess the accuracy of these measures, researchers used continuous glucose monitoring (CGM) in Ugandan patients with type 2 diabetes, including some with sickle cell trait, anemia, and renal impairment. Adult patients with type 2 diabetes for more than 12 months were recruited from two hospitals from July 2019 to March 2020. Patients had no insulin requirement for at least a year after diabetes diagnosis and no change in glucose-lowering therapy in the three months before recruitment. Asahi Kasei Pharma provided the glycated albumin assay used in the study without charge. Results were published April 27 by Diabetic Medicine.
Out of 213 patients recruited, 192 had at least five days of CGM data and were included in the study. Median CGM duration was 14 days. A total of 43 patients (22.4%) had hemoglobinopathies (42 with sickle cell trait HbAS and one with HbSC), 18 (9.4%) had anemia, and 12 (6.3%) had renal impairment. The median hemoglobin concentration among those with and without HbA1c-affecting conditions was 13.5 g/dL (8.38 mmol/L) and 14.3 (8.87 mmol/L) g/dL, respectively.
Overall, HbA1c, glycated albumin, and fructosamine measurements were similar to CGM results (r=0.88 [95% CI, 0.84 to 0.91], 0.84 [95% CI, 0.79 to 0.88], and 0.84 [95% CI, 0.79 to 0.88], respectively). For detecting those with mean CGM glucose level greater than 8 mmol/L (144 mg/dL), HbA1c had similar diagnostic accuracy to glycated albumin and fructosamine, even in those with conditions reported to affect HbA1c assessment. There was no evidence that sickle cell trait altered the relationship of HbA1c, fructosamine, or glycated albumin level with CGM results (P>0.3 for all). In patients with anemia compared to those without, glucose concentration was underestimated by both HbA1c and fructosamine relative to CGM. However, with glycated albumin, the difference from CGM results was not significantly different between those with anemia and those without.
The researchers noted that the study's inclusion of a modest number of participants with renal impairment and anemia meant that they could not determine the effects of mild versus severe conditions and could not exclude any important interactions in these subgroups. Also, they did not assess the impact of other conditions that may affect HbA1c reliability, such as glucose-6 phosphate dehydrogenase variants.
“Our findings suggest that [glycated albumin] and fructosamine are unlikely to have clinical utility for glucose monitoring over and above HbA1c testing, even in those with conditions reported to affect HbA1c validity,” they wrote. “Our results also suggest that sickle cell trait is not an important issue for interpretation of HbA1c testing in those with diabetes.”