Monitoring Progression of Diabetic Nephropathy

Abstract

Glomerular filtration rate (GFR, single bolus ⁵¹Cr-EDTA technique), serum creatinine and serum β₂-microglobulin concentrations were measured simultaneously in 49 insulin-dependent diabetics with diabetic nephropathy. GFR ranged from 148 to 23 ml/min/1.73 m². Inverse serum concentrations of creatinine and β₂-microglobulin showed a significant correlation with GFR over the whole range of values, r = 0.87 and r = 0.90, respectively (p <0.001). In the 31 patients with a GFR < 80 ml/min/1.73 m², serum concentration of creatinine and β₂-microglobulin were within the normal range in 12 and 9 patients, respectively. With GFR below 60 ml/min/1.73 m², all patients had elevated serum β₂-microglobulin concentrations, while 24% of the patients still had normal creatinine concentration. Linear regression analysis between log GFR and log serum β₂-microglobulin showed a better relationship than between log GFR and log serum creatinine, slope −0.90 and −0.57, respectively, p <0.01. A prospective study for up to 70 months was performed in 18 of the patients. The study showed a closer relationship between the individual rate of decline in log GFR and log serum β₂-microglobulin compared to log GFR versus log serum creatinine, p < 0.01. Neither serum creatinine nor serum β₂-microglobulin can be used as methods for screening of early impairment of renal function (GFR < 80 ml/min/1.73 m² in diabetic nephropathy. Our study suggests that serum β₂-microglobulin is more ideal endogenous marker for GFR estimation than serum creatinine. The accuracy and precision of serum β₂-microglobulin is better than serum creatinine in monitoring the individual rate of decline in kidney function in diabetic nephropathy.