Cystatin C is ready for clinical use

Abstract

The goal of this update is to raise awareness of clinical scenarios where cystatin C has clear and immediate benefits as an alternative glomerular filtration rate (GFR) biomarker to supplement creatinine. An additional goal is to focus the estimated GFR (eGFR) controversy onto medication prescribing for agents with narrow therapeutic windows where better GFR estimation will lead to improved medical care. Equations that include cystatin C predict GFR more accurately than serum creatinine in children, adults, and older adults with larger effects among persons who are acutely ill. Numerous studies have evaluated medication dosing based on either GFR estimate; vancomycin was the most frequently studied drug and its target level and elimination were better predicted by cystatin C. Overall, approaches to medication dosing and monitoring that include cystatin C concentrations have been shown to result in a better achievement of drug trough levels. Furthermore, cystatin C offers the opportunity to avoid the race coefficient that is required for any current creatinine-based eGFR equation, which has been appropriately criticized for introducing unnecessary imprecision, assumptions and values on GFR estimation. Hospital laboratories must make cystatin C available for clinical care to improve the safety and efficacy of medications that have narrow therapeutic windows.