Koo,
Yes, I read in several sources that the "normal" range of eGFR is 90 to something in the 120-135 mL/min/1.73m2. However, there seem to be a few different calculation methods: CKD-EPI, MDRD, Cockcroft-Gault Equation, etc. There are slight differences in each method, and the method used for the upper limit of normal of 120-135 mL/min/1.73m2 may be a different method than the Cockcroft-Gault method used in BETonMACE. For the MDRD equation, anything over 90 is assumed to be normal and this MDRD method is more suited for detecting CKD but underestimates the actual GFR in normal patients. As I detailed this for the Cockcroft-Gault, there can be some inflated eGFR values that get pretty high due to an artifact of a low creatinine measurement, for example. This doesn't necessarily mean that the kidney function and actual GFR is better in someone with an eGFR of 599 vs. 120 by the Cockcroft-Gault. It could simply be anor a limitation of a formula that isn't suited to dealing with certain parameters way outside of normal ranges.
BearDownAZ