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Kidney Week

Abstract: PO0520

Cystatin C Use in Clinical Practice

Session Information

Category: CKD (Non-Dialysis)

  • 2101 CKD (Non-Dialysis): Epidemiology, Risk Factors, and Prevention

Authors

  • Torres, Jennifer, DaVita Inc, Denver, Colorado, United States
  • Ennis, Jennifer L., Laboratory Corporation of America, Burlington, North Carolina, United States
  • McGill, Rita L., University of Chicago, Chicago, Illinois, United States
Background

Cystatin C is a filtration biomarker that can be used as an alternative for serum creatinine. The 2012 KDIGO guidelines advocate for the use of cystatin C to confirm the diagnosis of chronic kidney disease (CKD), but 9 years later it is not clear how this test is being used in clinical practice.

Methods

We examined 87,803 cystatin C levels obtained among 55,360 patients between 11/2011-6/2018 in the database of Laboratory Corporation of America Holdings (LabCorp®). The CKD-EPI cystatin equation was used to calculate the estimated GFR for each level. Descriptive analyses of patient age, sex, and ordering provider were constructed, and relationships between serum cystatin C and creatinine levels were examined with correlation analysis and linear regression.

Results

The mean age was 58±17;50.2% were women. Frequency of orders increased over time, from 6,323 tests in 2012, to 17,822 tests in 2017. Providers ordering cystatin C included: Internal/Family Medicine MDs (83%), radiologists (4%), mid-levels (4%), and 9% unknown. Cystatin C was ordered on patients with a wide range of estimated GFR values (Figure). Linear regression showed that 75% of the variation in cystatin C could be modeled if age, sex, BUN, and creatinine were known. Dispersion between actual and predicted cystatin was minimal at cystatin C levels ≤ 3.0 mg/L, representing estimated GFR values ≥ 15 mL/min/1.73m2.

Conclusion

Providers are ordering cystatin C with increasing frequency over time, for a variety of indications besides confirmation of borderline CKD. Cystatin can be modeled fairly reliably, using BUN, creatinine, sex, and age, for cystatin levels≤ 3.0 mg/L.