Swedko et al1 make a strong case for the limitations of serum creatinine in predicting or monitoring renal function, especially in elderly patients. All of us who provide primary care need to be aware of this important point.
They offer the Cockroft-Gault (C-G) equation as an alternative that is easy to calculate and that better approximates GFR. This equation was originally validated primarily for male patients and does not account for variables such as ethnicity. Further, in reviews by the National Kidney Foundation (NKF),1 only 75% of estimates of GFR using the C-G equation were within 30% of the measured GFR.
Bernheim S, Chen S, Gomez M, Jensen R, Kohler L, Love L, Villela T, Winscott M. A Better Alternative for Estimating Renal Function. Arch Intern Med. 2003;163(18):2248-2249. doi:10.1001/archinte.163.18.2248-a