480 - Implementation of Directly Reported eGFR in a Real-World Setting

Publication Number: 2468.480

Fatimah K. Hussain, University of Missouri-Kansas City School of Medicine, Kansas City, MO, United States; Darcy Weidemann, Children's Mercy Hospitals and Clinics, Kansas City, MO, United States

Background: Accurate estimation of glomerular filtration rate (eGFR) is essential for diagnosing and managing chronic kidney disease (CKD). Creatinine (Cr)-based eGFR is widely used but is influenced by muscle mass, growth, and diet, which can misrepresent kidney function. Cystatin C (CysC), a protein less influenced by body habitus, is recommended in pediatric populations to improve precision of eGFR estimates. Despite this, cystatin C remains underutilized, and little is known about how non-nephrology clinicians act on its results.

Objective: This study examines the use of cystatin C by non-nephrology providers, focusing on recognition of impaired eGFR, nephrology referral patterns, and medication management.

Design/Methods: Retrospective chart review of pediatric patients at Children’s Mercy Kansas City with paired Cr and CysC samples from March 2024 to January 2025. Demographic and clinical data, including serum Cr, CysC, and corresponding eGFR values, were collected. Concordant eGFR were defined as eGFRdiff = eGFRCysC -eGFRCr ± 15 mL/min/1.73m2. Positive discordance was noted when eGFRCysC was higher than eGFRCr and negative discordance was defined when eGFRCysC was lower than eGFRCr by 15 mL/min/1.73m2. Chart review was performed to assess CKD recognition, nephrology referral placement, and medication adjustment for kidney function. Descriptive statistics were used to summarize findings.

Results: Table 1 depicts selected variables of 108 study subjects, stratified by concordant or discordant eGFRs. A total of 69% of eGFRs were concordant, with a higher positive discordance of 21% and negative discordance of 9%. The highest utilization of CysC was observed in oncology and hepatology clinics. Recognition of impaired GFR was documented in the chart in 74 cases (63% of concordant GFR, 8% of positive discordant GFR, and 90% of negative discordant GFR). Referrals to nephrology were placed in 48% of encounters, with 36% of patients establishing care with nephrology. Medication adjustments were documented in 16 patients (15%), and 7 patients (6.5%) were started on new medications.

Conclusion(s): Although most providers recognized impaired kidney function and nearly half placed nephrology referrals, few patients had medication adjustments or new therapies initiated. Providers were more likely to recognize impaired GFR with negative discordance, perhaps because eGFR-CysC is directly presented in the EMR whereas eGFR-Cr must be intentionally ordered by providers. These findings reveal a gap between recognition and management, indicating a need for greater clinical integration of CysC results into treatment decisions.

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