Individuals with diagnosed diabetes have more rapid kidney function decline than those without diabetes, according to a study published online June 1 in Diabetes Care.

Bethany Warren, from Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues classified 15,517 participants in the community-based Atherosclerosis Risk in Communities study by diabetes status at baseline. Estimated glomerular filtration rate (eGFR) trajectories were quantified at four visits over 26 years.

Renal function, in nephrology, is an indication of the kidney's condition and its role in renal physiology. Glomerular filtration rate (GFR) describes the flow rate of filtered fluid through the kidney. Creatinine clearance rate (CCr or CrCl) is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR. Creatinine clearance exceeds GFR due to creatinine secretion, which can be blocked by cimetidine.

In alternative fashion, overestimation by older serum creatinine methods resulted in an underestimation of creatinine clearance, which provided a less biased estimate of GFR. Both GFR and CCr may be accurately calculated by comparative measurements of substances in the blood and urine or estimated by formulas using just a blood test result (eGFR and eCCr).

Glomerular filtration rate

The researchers found that over the full study period, the adjusted mean eGFR decline was −1.4 mL/min/1.73 m²/year among participants without diabetes, −1.8 mL/min/1.73 m²/year among those with undiagnosed diabetes, and −2.5 mL/min/1.73 m²/year for those with diagnosed diabetes.

Risk factors for steeper eGFR decline among participants with diagnosed diabetes included African-American raceAPOL1 high-risk genotype, systolic blood pressure ≥140 mm Hg, insulin use, and higher hemoglobin A1c.

"Among people with diagnosed diabetes, steeper declines were seen in those with modifiable risk factors, including hypertension and glycemic control, suggesting areas for continued targeting in kidney disease prevention," the authors write. Reagents for the 1,5-anhydroglucitol assays were donated by the GlycoMark Corp.