Performance of Panel-Estimated GFR Among Hospitalized Older Adults

Rationale & Objective: Older adults represent nearly half of all hospitalized patients and are vulnerable to inappropriate dosing of medications eliminated through the kidneys. However, few studies in this population have evaluated the performance of equations for estimating the glomerular filtration rate (GFR)-particularly those that incorporate multiple filtration markers. Study Design: Cross-sectional diagnostic test substudy of a randomized clinical trial. Setting & Participants: Adults >= 65 years of age presenting to the emergency department of Copenhagen University Hospital Amager and Hvidovre in Hvidovre, Denmark, between October 2018 and April 2021. Tests Compared: Measured GFR (mGFR) determined using 99mTc-DTPA plasma clearance compared with estimated GFR (eGFR) calcu-lated using 6 different equations based on creatinine; 3 based on creatinine and cystatin C combined; and 2 based on panels of markers including creatinine, cystatin C, 5 -trace protein (BTP) and/or 52-microglobulin (B2M). Outcome: The performance of each eGFR equation compared with mGFR with respect to bias, relative bias, inaccuracy (1-P3 0), and root mean squared error (RMSE). Results: We assessed eGFR performance for 106 patients (58% female, median age 78.3 years, median mGFR 62.9 mL/min/1.73 m2). Among the creatinine-based equations, the 2009 CKD-EPIcr equation yielded the smallest relative bias (+4.2%). Among the creatinine-cystatin C combination equations, the 2021 CKD-EPIcomb equation yielded the smallest relative bias (-3.4%), inaccuracy (3.8%), and RMSE (0.139). Compared with the 2021 CKD-EPIcomb, the CKD-EPIpanel equation yielded a smaller RMSE (0.136) but larger relative bias (-4.0%) and inaccuracy (5.7%). Limitations: Only White patients were included; only a subset of patients from the original clinical trial underwent GFR measurement; and filtration marker concentration can be affected by sub-clinical changes in volume status. Conclusions: The 2009 CKD-EPIcr, 2021 CKD-EPIcomb, and CKD-EPIpanel equations performed best and notably outperformed their respective full-age spectrum equations. The addition of cystatin C to creatinine-based equations improved performance, while the addition of BTP and/or B2M yielded minimal improvement. Funding: Grants from public sector industry (Amgros I/S) and government (Capital Region of Denmark). Trial Registration: Registered at ClinicalTrials. gov with registration number NCT03741283.