Discrepancies in the RIFLE classification are due to the method used to assess the level of derangement of kidney function.

Purpose: We hypothesized that RIFLE based on creatinine clearance (CrCl) is superior to that based on serum creatinine (sCr) or Cockroft-Gault (C-G) because it is an earlier marker of kidney dysfunction.

Materials And Methods: At day 3 of admission, we compared the RIFLE based on sCr, C-G, and CrCl with 28-day mortality and development of RIFLE-F during intensive care unit stay.

Results: Percentages in the RIFLE levels were similar for the 3 estimates, but the patients included in each level were different; with CrCl as the reference, κ statistic was 0.