Cystatin C is a 13-kDa
cysteine protease inhibitor that satisfies many of the criteria required of a marker of glomerular filtration rate. It can be readily measured in laboratories using automated, standardised immunoassays. Hitherto there has been reluctance to adopt
cystatin C measurement in the assessment of kidney function, despite demonstrated superiority compared to the current standard of practice, serum
creatinine. This may be due to increased direct
reagent costs. Recent strong evidence has confirmed the superior ability of
cystatin C compared to
creatinine to predict risk of a range of poor outcomes (including
kidney failure, cardiovascular events and mortality) among patients with
chronic kidney disease. On the back of this, national and international guidelines including those of the National Institute for Health and Clinical Excellence have recommended the use of
cystatin C to risk stratify individuals with mild to moderately reduced glomerular filtration rate and no
albuminuria.
Cystatin C presents an opportunity for laboratories to engage with their users in developing clinical pathways which will usefully focus
chronic kidney disease management on those most likely to benefit while reassuring patients at low risk.