Commentary: clinical diagnostic use of cystatin C.

Clinicians recognize and compensate for limitations in estimating the glomerular filtration rate (GFR) using serum creatinine (sCr) measurements by the use of timed collections and mathematical manipulations of sCr. These limitations stem from that fact that sCr is affected by nonrenal influences, including muscle mass and disease state. In addition, sCr may not be sensitive enough to detect minimal declines in GFR in those patient populations in which it is important to recognize early decline. This brief review describes the limitations of sCr, and examines the contribution that sCysC may be able to make in the early recognition of declining renal function. The physiology of CysC is presented, as are the results of clinical investigations that suggest sCysC is in many instances superior to sCr in the recognition of early decline in renal function. Certain exceptions to this are noted. Copyright 2004 Wiley-Liss, Inc.