Comparison of the Rate of Renal Function Decline in NonProteinuric Patients With and Without Diabetes

Abstract

Background: Patients with diabetes and chronic kidney disease (CKD) without proteinuria are often believed to have a cause of CKD other than diabetes. It was hypothesized that if this is true, the rate of renal function decline should be similar among nonproteinuric patients with and without diabetes.

Methods: Patients seen in the nephrology, endocrinology and general internal medicine clinics at the Medical University of South Carolina (MUSC) between 2008 and 2012 with hypertension and diabetes were identified by ICD9 diagnosis codes. Patients with less than 2 measures of serum creatinine, without urine studies over the study period and with proteinuria were excluded. Four hundred seventy-two patients met the inclusion and exclusion criteria and had an initial estimated glomerular filtration rate (eGFR) between 35 and 80 mL/min per 1.73 m2. The annual rate of decline in eGFR was estimated for each patient from the lowest eGFR in each year by fitting a regression model with random intercept and slope.

Results: In unadjusted analyses, the rate of eGFR decline was greater in patients with diabetes than without diabetes (-0.71 versus -0.30 mL · min(-1) · yr(-1), P = 0.03). After adjusting for age, race, sex, baseline eGFR and use of renin-angiotensin-aldosterone system blockade, the rate of decline was still greater among patients with diabetes than among those without diabetes (-0.68 versus -0.36 mL · min(-1) · yr(-1), P = 0.03).

Conclusions: Patients with diabetes had more rapid decline in kidney function compared with individuals without diabetes, despite the absence of proteinuria. These results suggest that even in the absence of proteinuria, diabetes may be associated with CKD.

Figure 1

Patient selection flow chart. 5035 patients were identified in the initial search of the electronic record who were seen in the nephrology, endocrinology or general internal medicine clinics between 2008 and 2012, with an estimated glomerular filtration rate (eGFR) greater than or equal to 35 mL/min/1.73 m2. From this group we selected 472 patients who met all inclusion and exclusion criteria for analysis of the rate of decline of eGFR.

Figure 2

Distribution of slopes of eGFR decline (mL/min/year) in the total population.

Figure 3

Figure 3a. Rate of eGFR change in patients with and without diabetes (DM) prior to adjustment. In diabetic group the slope is −0.71 mL/min/year 95% CI (−0.93, −0.49). In non-diabetic group the slope is −0.30 mL/min/year 95% CI (−0.60, 0.00); P = 0.03. Figure 3b. Rate of eGFR change in patients with and without diabetes (DM) after adjustment. Adjustment was made for baseline eGFR, age, race, gender, ACE inhibitors, ARBs, spironolactone. In diabetic group the slope is −0.68 mL/min/year 95% CI (−0.85, −0.51). In non-diabetic group the slope is −0.36 mL/min/year 95% CI (−0.59, −0.13); P = 0.03.

Figure 3

Figure 3a. Rate of eGFR change in patients with and without diabetes (DM) prior to adjustment. In diabetic group the slope is −0.71 mL/min/year 95% CI (−0.93, −0.49). In non-diabetic group the slope is −0.30 mL/min/year 95% CI (−0.60, 0.00); P = 0.03. Figure 3b. Rate of eGFR change in patients with and without diabetes (DM) after adjustment. Adjustment was made for baseline eGFR, age, race, gender, ACE inhibitors, ARBs, spironolactone. In diabetic group the slope is −0.68 mL/min/year 95% CI (−0.85, −0.51). In non-diabetic group the slope is −0.36 mL/min/year 95% CI (−0.59, −0.13); P = 0.03.

Figure 4

Figure 4a. Rate of eGFR change among diabetic patients with a baseline eGFR of 60 mL/min/1.73 m² or lower versus those with a baseline eGFR greater than 60 (−2.06 mL/min/year, 95% CI (−2.38, −1.74) vs. 0.07 mL/min/year, 95% CI (−0.18, 0.32), P < 0.0001). Figure 4b. Rate of eGFR change among non diabetic patients with a baseline eGFR of 60 mL/min/1.73 m² or lower versus those with a baseline eGFR greater than 60 (−1.61 mL/min/year, 95% CI (−2.00, −1.22) vs. 0.52 mL/min/year, 95% CI (0.22, 0.82), P < 0.001).

Figure 4

Figure 4a. Rate of eGFR change among diabetic patients with a baseline eGFR of 60 mL/min/1.73 m² or lower versus those with a baseline eGFR greater than 60 (−2.06 mL/min/year, 95% CI (−2.38, −1.74) vs. 0.07 mL/min/year, 95% CI (−0.18, 0.32), P < 0.0001). Figure 4b. Rate of eGFR change among non diabetic patients with a baseline eGFR of 60 mL/min/1.73 m² or lower versus those with a baseline eGFR greater than 60 (−1.61 mL/min/year, 95% CI (−2.00, −1.22) vs. 0.52 mL/min/year, 95% CI (0.22, 0.82), P < 0.001).