Abstract: SA-PO410

Estimated Glomerular Filtration Rate by Serum Creatinine Lacks Accuracy and Precision in Older Adults with and without Type 1 Diabetes: Results from the Canadian Study of Longevity in Type 1 Diabetes

Session Information

Category: Chronic Kidney Disease (Non-Dialysis)

  • 302 CKD: Estimating Equations, Incidence, Prevalence, Special Populations

Authors

  • Scarr, Daniel, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
  • Keenan, Hillary A., Joslin Diabetes Center, Boston, Massachusetts, United States
  • Brent, Michael, University of Toronto, Toronto, Ontario, Canada
  • Paul, Narinder, University of Toronto, Toronto, Ontario, Canada
  • Bril, Vera, University of Toronto, Toronto, Ontario, Canada
  • Cherney, David, University of Toronto, Toronto, Ontario, Canada
  • Perkins, Bruce A., University of Toronto, Toronto, Ontario, Canada
  • Lovblom, Leif Erik, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
  • Bjornstad, Petter, Children's Hospital Colorado, Aurora, Colorado, United States
  • Lovshin, Julie A, University of Toronto, Toronto, Ontario, Canada
  • Farooqi, Mohammed A. Malik, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
  • Boulet, Genevieve, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
  • Orszag, Andrej, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
  • Lytvyn, Yuliya, University of Toronto, Toronto, Ontario, Canada
  • Weisman, Alanna, Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
Background

Estimates of glomerular filtration rate (eGFR) by serum creatinine are routinely used for clinical assessment of kidney function, however eGFR is considered inaccurate until GFR <60mL/min/1.73m2. Accurate ascertainment of eGFR is important to identify kidney disease. We aimed to evaluate the performance of creatinine-based equations compared to GFR by inulin clearance in older adults with and without type 1 diabetes (T1D).

Methods

Sixty-six adults with ≥50yr T1D duration and 73 non-diabetic controls from age/sex-matched subgroups (65±8yr and 77[55%] were female) underwent measurement of GFR by inulin clearance (mGFR) and eGFR was calculated by serum creatinine using the MDRD (eGFRMDRD) and CKD-EPI (eGFRCKD-EPI) equations. In T1D, eGFR and mGFR were measured under clamped euglycemia (4-6mmol/L). Equation performance was evaluated using bias (mean difference), precision (SD), and accuracy (inaccuracy defined as the proportion of eGFR that differed by >20% of mGFR) metrics.

Results

In the 139 participants mean mGFR was 104±18mL/min/1.73m2 (range: 70-154mL/min/1.73m2) and was not different between T1D (103±17mL/min/1.73m2) and controls (105±19mL/min/1.73m2, p=0.39). Both equations significantly underestimated mGFR with bias −14.9mL/min/1.73m2 (p<0.001) for eGFRMDRD and −15.9mL/min/1.73m2 for eGFRCKD-EPI (p<0.001); bias was similar between equations (p=0.15). Precision was similar between eGFRMDRD (SD 17.2mL/min/1.73m2) and eGFRCKD-EPI (SD 16.5mL/min/1.73m2, p=0.63). Inaccuracy was similar between eGFRMDRD (32.4%) and eGFRCKD-EPI (37.4%, p=0.13). Both equations demonstrated greater bias and were less accurate across higher ranges of mGFR (60-89, 90-119, and ≥120mL/min/1.73m2, p<0.001 for all comparisons). Results were similar between T1D and controls.

Conclusion

Creatinine-based eGFR substantially underestimated mGFR, lacked precision and accuracy, and had lower performance at higher ranges of mGFR. Better measures of kidney function in older adults are needed for research and clinical practice.