Effect of chronic kidney disease on A1C in individuals being screened for diabetes

• HbA1c is used for the diagnosis of type 2 diabetes but the validity in kidney disease is unknown.
• Stage 4 and 5 kidney disease is rare (<0.1%) in patients being screened for diabetes.
• Stage 3 kidney disease patients are older and have higher HbA1c measurements than stage <3.
• Multivariable regression analysis shows that kidney disease stage 3 does not affect HbA1c.
• Increasing age, South Asian ethnicity and lower haemoglobin were associated with higher HbA1c.

ObjectiveGlycated haemoglobin (A1C) has been recommended for the diagnosis of type 2 diabetes mellitus. Chronic kidney disease (CKD) is reported to increase A1C. The prevalence of CKD and its association with A1C as a diagnostic test for type 2 diabetes screening in a community population was studied.Research design and methodsAge, gender, ethnicity (white/South Asian), haemoglobin, A1C, fasting glucose and fructosamine were compared in participants with estimated glomerular filtration rate (eGFR) 30–59 (CKD 3) and ≥60 ml/min/1.73 m2 using chi-squared or t-tests. Multivariable linear regression analyses were performed with A1C as the dependent variable; remaining variables were forced into a model to identify correlates with A1C. Data were parametric and expressed as means.ResultsOf 949 participants 83.7% had eGFR ≥60, 16.3% had CKD 3 and only 2 had eGFR <30 (CKD ≥4). Compared with eGFR ≥60, patients with CKD 3 were older [p < 0.001], had higher A1C [6.0% vs. 5.8%, p < 0.001], fasting glucose [5.4 vs. 5.2 mmol/L, p = 0.003] and fructosamine [233.7 vs. 225.8 μmol/L, p < 0.001] but lower haemoglobin [p = 0.006]. After adjustment, gender and CKD stage were not associated with A1C. A1C was associated (p < 0.05) positively with age, South Asian ethnicity, fasting glucose and fructosamine and inversely with haemoglobin levels.ConclusionsSevere CKD (stage ≥4) is rare in primary care patients being screened for type 2 diabetes and its impact on A1C could not be evaluated. Although A1C is higher among patients with CKD stage 3 compared to those with eGFR ≥60, this appeared to be due to the confounding effect of other variables rather than the presence of CKD.