Problems with serum creatinine measurement
Although commonly used, serum creatinine (sCr) is not an ideal marker of kidney function since it is affected by age, sex and body mass. In fact, creatinine levels often remain within the normal range until kidney function is significantly impaired, especially in older individuals or those with low muscle mass.

Alternatives to creatinine measurement
Glomerular filtration rate (GFR) is the gold standard measure of kidney function, and, in adults, can be easily and accurately estimated using the CKD-EPI GFR equation or the abbreviated MDRD GFR equation (Estimation of GFR). Although creatinine clearance measurements, as measured using a 24 hour urine collection, also estimate kidney function, they are no more accurate than estimated GFR and are cumbersome to obtain.           

For further information please see “Frequently asked questions about GFR estimates                

For more information about random urine ACR please see the online CKD Pathway.