Estimating Glomerular Filtration Rate Calculated by Serum Creatinine Lacks Precision and Accuracy in Adults with Type 2 Diabetes with Preserved Renal Function
Authors: LOVSHIN JULIE A. , LOVBLOM LEIF ERIK , BJORNSTAD PETTER , LYTVYN YULIYA , RAJASEKERAN HARINDRA , SCARR DANIEL , PERKINS BRUCE A. , CHERNEY DAVID 
Published: June 2018

We evaluated the performance of creatinine-based estimating equations for glomerular filtration rate (GFR) in adults with type 2 diabetes without nephropathy compared to measured GFR by gold-standard inulin clearance methods. mGFR was performed 4 times over the course of a 1 month treatment period in the context of a small randomized placebo-controlled trial measuring the intrarenal hemodynamics function responses to the dipeptidyl peptidase 4 inhibitor sitagliptin. Thirty-two adults with type 2 diabetes (randomized 1:1 to placebo or sitagliptin) completed the trial, and all participants underwent mGFR by inulin clearance and GFR estimated by serum creatinine using the MDRD (eGFRMDRD) and CKD-EPI (eGFRCKD-EPI). Performance of eGFR equations was evaluated using measurements of bias (mean difference), precision (standard deviations [SD]), and inaccuracy (defined as the proportion of eGFR that differed by &gt;20% of mGFR). The effects of treatment and time on bias were evaluated using linear mixed effects models. Mean±SD age, diabetes duration, HbA1c, and BMI was 60±8 years, 9±7 years, 7.2±0.8%, and 31.0±6.2 kg/m2, respectively, and 12(38%) participants were female. At baseline, mean mGFR was 113±24, mean eGFRMDRD was 93±12, and mean eGFRCKD-EPI was 94±9, all in mL/min/1.73m2. When all 128 observations (32 participants measured 4 times) were evaluated, both equations substantially underestimated mGFR. For the eGFRMDRD, mean bias was -21.5 mL/min/1.73m2, precision was 22.7 mL/min/1.73m2, and 46% of observations differed by more than 20%. Results were similar for eGFRCKD-EPI. No time or treatment effects on bias were observed. In adults with type 2 diabetes, eGFR equations underestimated mGFR, lacked precision and accuracy, and had lower performance at higher ranges of mGFR. More accurate measures of kidney function may improve clinical decision-making in adults with type 2 diabetes.

Disclosure
J.A. Lovshin: Other Relationship; Self; AstraZeneca. Consultant; Self; Novo Nordisk Inc.. Research Support; Self; Sanofi, Merck Sharp & Dohme Corp.. Other Relationship; Self; Novo Nordisk Inc.. L. Lovblom: None. P. Bjornstad: Consultant; Self; Boehringer Ingelheim GmbH. Y. Lytvyn: None. H. Rajasekeran: None. D. Scarr: None. B.A. Perkins: Advisory Panel; Self; Boehringer Ingelheim GmbH. Research Support; Self; Boehringer Ingelheim GmbH, Novo Nordisk Inc.. Advisory Panel; Self; Novo Nordisk Inc., Abbott. Speaker's Bureau; Self; Abbott, Janssen Pharmaceuticals, Inc.. Advisory Panel; Self; Insulet Corporation. Speaker's Bureau; Self; Insulet Corporation, Dexcom, Inc. D. Cherney: Consultant; Self; AbbVie Inc.. Other Relationship; Self; AstraZeneca, Boehringer Ingelheim GmbH, Eli Lilly and Company. Consultant; Self; Sanofi. Other Relationship; Self; Merck & Co., Inc.. Consultant; Self; Mitsubishi Tanabe Pharma Corporation. Other Relationship; Self; Janssen Pharmaceuticals, Inc..