A comparison of observed versus estimated baseline creatinine for determination of RIFLE class in patients with acute kidney injury

Sean M. Bagshaw, Shigehiko Uchino, Dinna Cruz, Rinaldo Bellomo, Hiroshi Morimatsu, Stanislao Morgera, Miet Schetz, Ian Tan, Catherine Bouman, Etienne MacEdo, Noel Gibney, Ashita Tolwani, Heleen M. Oudemans-Van Straaten, Claudio Ronco, John A. Kellum

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Background. The RIFLE classification scheme for acute kidney injury (AKI) is based on relative changes in serum creatinine (SCr) and on urine output. The SCr criteria, therefore, require a pre-morbid baseline value. When unknown, current recommendations are to estimate a baseline SCr by the MDRD equation. However, the MDRD approach assumes a glomerular filtration rate of ∼75 mLmin1.73 m 2 . This method has not been validated.Methods. Data from the Beginning and Ending Supportive Therapy for the Kidney (BEST Kidney) study, a prospective observational study from 54 ICUs in 23 countries of critically ill patients with severe AKI, were analysed. The RIFLE class was determined by using observed (o) pre-morbid and estimated (e) baseline SCr values. Agreement was evaluated by correlation coefficients and Bland-Altman plots. Sensitivity analysis by chronic kidney disease (CKD) status was performed.Results. Seventy-six percent of patients (n = 1327) had a pre-morbid baseline SCr, and 1314 had complete data for evaluation. Forty-six percent had CKD. The median (IQR) values were 97 μmolL (79-150) for oSCr and 88 μmolL (71-97) for eSCr. The oSCr and eSCr determined at ICU admission and at study enrolment showed only a modest correlation (r = 0.49, r = 0.39). At ICU admission and study enrolment, eSCr misclassified 18.8 and 11.7 of patients as having AKI compared with oSCr. Exclusion of CKD patients improved the correlation between oSCr and eSCr at ICU admission and study enrolment (r = 0.90, r = 0.84) resulting in 6.6 and 4.0 being misclassified, respectively.Conclusions. While limited, estimating baseline SCr by the MDRD equation when pre-morbid SCr is unavailable would appear to perform reasonably well for determining the RIFLE categories only if and when pre-morbid GFR was near normal. However, in patients with suspected CKD, the use of MDRD to estimate baseline SCr overestimates the incidence of AKI and should not likely be used. Improved methods to estimate baseline SCr are needed.

Original languageEnglish
Pages (from-to)2739-2744
Number of pages6
JournalNephrology Dialysis Transplantation
Volume24
Issue number9
DOIs
Publication statusPublished - 1 Sep 2009

Cite this