Testing Kidney Function Using an Alternative Filtration Marker

Diabetic kidney disease accounts for 40 percent of prevalent chronic kidney disease (CKD) and 50 percent of incident end-stage renal disease (ESRD). Individuals with diabetes and CKD are at an even greater risk of morbidity and mortality. In practice, kidney function is estimated rather than measured; estimated glomerular filtration rate (eGFR) using serum creatinine is the most common method of testing the kidney's function. When using serum creatinine to measure kidney function, age, muscle mass, sex and race are factors in kidney function. A valid alternative to using serum creatinine would be to use cystatin-C, an endogenous protein produced by almost all nucleated cells. Cystatin-C is less affected by age, race and muscle mass; however, BMI, diabetes and inflammation may affect cystatin levels.

There have been many previous studies concerning the effectiveness of eGFR. A recent study analyzed true glomerular filtration rate (GFR) versus urinary creatinine clearance and found that the common method of estimating GFR demonstrated poor precision in critical care patients. Many researchers are analyzing more accurate and precise methods to measure kidney

This study analyzed participants, aged 20 and older with available results of cystatin C. Researchers compared the performance of eGFR using cystatin-C to eGFR using creatinine in the identification of kidney function in diabetic participants. There were 4,457 participants with preserved or reduced kidney function that were analyzed in this study; 778 of the participants had diabetes.

Of the 778 participants with diabetes, the prevalence of reduced kidney functions was greatest among the estimated glomerular filtration rate using cystatin (eGFR). There was a 22 percent prevalence of reduced kidney function using cystatin-C and a 16.5 percent prevalence using creatinine. Other results showed more persons with diabetes were re-classified from preserved kidney function using creatinine to reduced kidney function using cystatin-C. There was strong association between lower eGFR and higher prevalence of complications also.

In conclusion, this study found that using cystatin-C filtration when estimating glomerular filtration rate leads to more diabetic patients being classified with reduced kidney function than by using creatinine filtration as an estimator.