Diagnostics and techniquesSerum cystatin C as a marker of glomerular filtration rateMadero, Magdalena; Sarnak, Mark J; Stevens, Lesley AAuthor Information Division of Nephrology, Tufts-New England Medical Center, Boston, Massachusetts, USA Correspondence to Lesley A. Stevens, MD, MS, 750 Washington St, Box 391, Boston MA 02111, USA Tel: +1 617 636 2569; fax: +1 617 636 5740; e-mail: [email protected] Current Opinion in Nephrology and Hypertension: November 2006 - Volume 15 - Issue 6 - p 610-616 doi: 10.1097/01.mnh.0000247505.71915.05 Buy Metrics Abstract Purpose of review Glomerular filtration rate is widely accepted as the best overall measure of kidney function. Currently available methods to estimate glomerular filtration rate have strengths and limitations. Cystatin C is a novel endogenous filtration marker being considered as a potential replacement for serum creatinine. This review summarizes the currently available glomerular filtration rate estimating equations based on cystatin C and the literature comparing cystatin C and creatinine as filtration markers. Recent findings In most cystatin C estimating equations, inclusion of age and sex did not substantially improve their performance. Equations yield different glomerular filtration rate estimates for the same level of cystatin C. Variation among equations may be due to differences among the assays or populations in the individual studies. Studies comparing cystatin C with creatinine or creatinine-based estimating equations show heterogeneous results, with some showing improved performance and others showing equivalent performance even in similar populations. These heterogeneous results may be due to inappropriate comparisons between equations developed in one population with those developed in another, or to the differences between assays or population characteristics. Summary Cystatin C shows promise as an alternative to serum creatinine but several important questions remain before it can be recommended for use in clinical practice. © 2006 Lippincott Williams & Wilkins, Inc.