Kidney Week

Abstract: TH-PO1120

Use of Cystatin C vs. Creatinine for Intravenous Vancomycin Dosing in Inpatients

Session Information

• CKD: Therapies, Innovations, and Insights
  November 06, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: CKD (Non-Dialysis)

• 2302 CKD (Non-Dialysis): Clinical, Outcomes, and Trials

Authors

• Potok, O. Alison, University of California San Diego, La Jolla, California, United States

O. Alison Potok, MD

• Yon, Cal, Veterans Affairs San Diego Healthcare System, San Diego, California, United States

Cal Yon

• Awdishu, Linda, Veterans Affairs San Diego Healthcare System, San Diego, California, United States

Linda Awdishu, PharmD, MA, FASN

• Ix, Joachim H., University of California San Diego, La Jolla, California, United States

Joachim H. Ix, MD, FASN

• Shlipak, Michael, University of California San Francisco, San Francisco, California, United States

Michael Shlipak, MD, MPH

• Rifkin, Dena E., University of California San Diego, La Jolla, California, United States

Dena E. Rifkin, MD

Background

Creatinine clearance is often the method of choice to assess glomerular filtration rate (GFR) in order to modify drug dosing. However, cystatin C may be a better marker of GFR than creatinine, especially in in-patients where muscle mass is often diminished. We assessed whether cystatin C eGFR explained over or underdosing of vancomycin.

Methods

Veterans hospitalized at VA San Diego receiving IV vancomycin for any clinical indication were recruited between 10/2023 and 03/2025. Participants with acute kidney injury (increase in serum creatinine by >= 0.3 from baseline), end stage kidney disease (dialysis or transplant), weight < 40 kg or BMI > 40 kg/m² were excluded. Vancomycin dosing intervals were determined by pharmacy staff using creatinine-based measures alone. Cystatin C was measured concurrent with creatinine in venous blood samples drawn prior to vancomycin initiation. Of 72 participants enrolled, the final analytic sample included 52 who had vancomycin trough levels measured. The primary outcome was the distance to target vancomycin level (DTT) defined by measured vancomycin trough (before the 4^th dose) minus the goal trough. Linear regression was used to assess the relationship between eGFRcys and DTT.

Results

Mean (standard deviation) age was 66 (15) years, 96% were men, 37% were non-white. Mean (SD) creatinine clearance was 99 (46) mL/min, eGFRcr was 85 (24) while eGFRcys was 53 (22) mL/min/1.73m². Mean (SD) maximum vancomycin target level was 18 (2) and measured vancomycin trough was 16 (5) mcg/mL. Mean (SD) DTT was 0.74 (5.2) mcg/mL. For every 10 mL/min/1.73m² decrement in eGFRcys the DTT vancomycin level was 0.93 mcg/mL higher, demonstrating that vancomycin was over-dosed more frequently, on average, as eGFRcys lowered (Fig 1.). This relationship persisted even after adjusting for creatinine-based GFR.

Conclusion

Using cystatin C in addition to creatinine to assess kidney function may improve dosing and help achieve the desired vancomycin trough level in a cohort of hospitalized veterans.

Funding

• NIDDK Support

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025c85gzxqy