HbA1c valid marker of blood glucose in anemia or CKD
medwireNews: The presence of mild-to-moderate anemia or chronic kidney disease (CKD) does not have a clinically significant effect on the interpretation of glycated hemoglobin (HbA1c) as a marker of glycemic control, Danish research shows.
It therefore “seems justified to use HbA1c without adjustment in primary care,” write Rikke Borg (University of Copenhagen) and colleagues in Diabetic Medicine.
However, they also note that “the validity of HbA1c deserves further attention” in more severe cases of anemia and CKD.
The researchers assessed the relationship between fasting plasma glucose (FPG) and HbA1c in 198,346 individuals (47.5% men) registered in a Danish primary care database.
Overall, they found that this relationship matched that observed in the A1c-Derived Average Glucose (ADAG) study, in which the association between HbA1c and average blood glucose concentrations was originally validated.
Nonetheless, Borg and team point out that a number of clinical conditions, including anemia and CKD, could alter the relationship between blood glucose and HbA1c by affecting erythropoiesis or the lifespan of erythrocytes.
They therefore stratified the data according to hemoglobin level and estimated glomerular filtration rate (eGFR).
In this analysis, the FPG–HbA1c relationship was unaffected in individuals with mild-to-moderate CKD and mild-to-moderate anemia, but changed in cases of severe hyperglycemia that was accompanied by either moderate-to-severe CKD (eGFR below 45 mL/min per 1.73 m2) or severe anemia (hemoglobin below 81 g/L).
Specifically, when HbA1c was above 11.3% (100 mmol/mol) and eGFR was below 50 mL/min per 1.73 m2, FPG was overestimated by 2–3 mmol/L. Conversely, when HbA1c was between 8.6 and 11.3% (70–100 mmol/mol) and hemoglobin was 81 g/L (5.0 mmol/L), FPG was underestimated by 2–3 mmol/L.
This degree of over- or underestimation of FPG, exclusively in people with severe anemia or severe kidney impairment, “is likely to have only limited clinical implications,” that are “below the threshold of a minimally important difference,” Borg et al remark.
They add that only 3.5% of individuals had moderately or severely impaired kidney function and just 0.11% had severe anemia “suggesting that HbA1c can be trusted” in primary care.
“Our findings should therefore reassure the clinician worried about the use of HbA1c in mild to moderate anaemia and CKD,” the team concludes.
By Laura Cowen
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