HbA1c variability as an independent correlate of nephropathy, but not retinopathy, in patients with type 2 diabetes: The renal insufficiency and cardiovascular events (RIACE) Italian Multicenter Study

OBJECTIVE-To examine the association of hemoglobin (Hb) A1c variability with microvascular complications in the large cohort of subjects with type 2 diabetes from the Renal Insufficiency And Cardiovascular Events (RIACE) Italian Multicenter Study. RESEARCH DESIGNANDMETHODS-Serial (3-5) HbA1c values collected in a 2-year period before enrollment were available from 8,260 subjects from 9 centers (of 15,773 patients from 19 centers). HbA1c variability was measured as the intraindividual SD of 4.52 ± 0.76 values. Diabetic retinopathy (DR) was assessed by dilated funduscopy. Chronic kidney disease (CKD) was defined based on albuminuria, as measured by immunonephelometry or immunoturbidimetry, and estimated glomerular filtration rate (eGFR) was calculated from serum creatinine. RESULTS-Median and interquartile range of average HbA1c (HbA1c-MEAN) and HbA1c-SD were 7.57% (6.86-8.38) and 0.46% (0.29-0.74), respectively. The highest prevalence of microalbuminuria, macroalbuminuria, reduced eGFR, albuminuric CKD phenotypes, and advanced DR was observed when bothHbA 1c parameters were above themedian and the lowest when bothwere below the median. Logistic regression analyses showed that HbA1c-SD adds toHbA1c-MEAN as an independent correlate of microalbuminuria and stages 1-2 CKD and is an independent predictor of macroalbuminuria, reduced eGFR, and stages 3-5 albuminuric CKD, whereas HbA1c-MEAN is not. The opposite was found for DR, whereas neither HbA1c-MEAN nor HbA 1c-SD affected nonalbuminuric CKD. CONCLUSIONS-In patients with type 2 diabetes, HbA1c variability affects (albuminuric) CKD more than average HbA1c, whereas only the latter parameter affects DR, thus suggesting a variable effect of these measures on microvascular complications.