Dataset Information

Serum Creatinine Back-Estimation in Cardiac Surgery Patients: Misclassification of AKI Using Existing Formulae and a Data-Driven Model.

ABSTRACT: A knowledge of baseline serum creatinine (bSCr) is mandatory for diagnosing and staging AKI. With often missing values, bSCr is estimated by back-calculation using several equations designed for the estimation of GFR, assuming a "true" GFR of 75 ml/min per 1.73 m(2). Using a data set from a large cardiac surgery cohort, we tested the appropriateness of such an approach and compared estimated and measured bSCr. Moreover, we designed a novel data-driven model (estimated serum creatinine [eSCr]) for estimating bSCr. Finally, we analyzed the extent of AKI and mortality rate misclassifications.Data for 8024 patients (2833 women) in our cardiac surgery center were included from 1997 to 2008. Measured and estimated bSCr were plotted against age for men and women. Patients were classified to AKI stages defined by the Kidney Disease Improving Global Outcomes (KDIGO) group. Results were compared with data from another cardiac surgery center in Zurich, Switzerland.The Modification of Diet in Renal Disease and the Chronic Kidney Disease Epidemiology Collaboration formulae describe higher estimated bSCr values in younger patients, but lower values in older patients compared with the measured bSCr values in both centers. The Pittsburgh Linear Three Variables formula correctly describes the increasing bSCr with age, however, it underestimates the overall bSCr level, being in the range of the 25% quantile of the measured values. Our eSCr model estimated measured bSCr best. AKI stage 1 classification using all formulae, including our eSCr model, was incorrect in 53%-80% of patients in Vienna and in 74%-91% in Zurich; AKI severity (according to KDIGO stages) and also mortality were overestimated. Mortality rate was higher among patients falsely classified into higher KDIGO stages by estimated bSCr.bSCr values back-estimated using currently available eGFR formulae are inaccurate and cannot correctly classify AKI stages. Our model eSCr improves the prediction of AKI but to a still inadequate extent.

SUBMITTER: Bernardi MH

PROVIDER: S-EPMC4791819 | biostudies-other | 2016 Mar

REPOSITORIES: biostudies-other

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Serum Creatinine Back-Estimation in Cardiac Surgery Patients: Misclassification of AKI Using Existing Formulae and a Data-Driven Model.

Bernardi Martin Hermann MH Schmidlin Daniel D Ristl Robin R Heitzinger Clemens C Schiferer Arno A Neugebauer Thomas T Wrba Thomas T Hiesmayr Michael M Druml Wilfred W Lassnigg Andrea A

Clinical journal of the American Society of Nephrology : CJASN 20160122 3

<h4>Background and objectives</h4>A knowledge of baseline serum creatinine (bSCr) is mandatory for diagnosing and staging AKI. With often missing values, bSCr is estimated by back-calculation using several equations designed for the estimation of GFR, assuming a "true" GFR of 75 ml/min per 1.73 m(2). Using a data set from a large cardiac surgery cohort, we tested the appropriateness of such an approach and compared estimated and measured bSCr. Moreover, we designed a novel data-driven model (est ...[more]

PMID: 26801479

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Project description:Background and objectivesAKI is a risk factor for development or worsening of CKD. However, diagnosis of renal dysfunction by serum creatinine could be confounded by loss of muscle mass and creatinine generation after critical illness.Design, setting, participants, & measurementsA retrospective, single center analysis of serum in patients surviving to hospital discharge with an intensive care unit admission of 5 or more days between 2009 and 2011 was performed.ResultsIn total, 700 cases were identified, with a 66% incidence of AKI. In 241 patients without AKI, creatinine was significantly lower (P<0.001) at hospital discharge than admission (median, 0.61 versus 0.88 mg/dl; median decrease, 33%). In 160 patients with known baseline, discharge creatinine was significantly lower than baseline in all patients except those patients with severe AKI (Kidney Disease Improving Global Outcomes category 3), who had no significant difference. In a multivariable regression model, median duration of hospitalization was associated with a predicted 30% decrease (95% confidence interval, 8% to 45%) in creatinine from baseline in the absence of AKI; after allowing for this effect, AKI was associated with a 29% (95% confidence interval, 10% to 51%) increase in predicted hospital discharge creatinine. Using a similar model to exclude the confounding effect of prolonged major illness on creatinine, 148 of 700 patients (95% confidence interval, 143 to 161) would have eGFR<60 ml/min per 1.73 m(2) at hospital discharge compared with only 63 of 700 patients using eGFR based on unadjusted hospital creatinine (a 135% increase in potential CKD diagnoses; P<0.001).ConclusionCritical illness is associated with significant falls in serum creatinine that persist to hospital discharge, potentially causing inaccurate assessment of renal function at discharge, particularly in survivors of AKI. Prospective measurements of GFR and creatinine generation are required to confirm the significance of these findings.

Project description:BackgroundThe primary aim of this study was to compare the sensitivity and rapidity of acute kidney injury (AKI) detection by cystatin C level relative to creatinine level after cardiac surgery.Study designProspective cohort study.Settings & participants1,150 high-risk adult cardiac surgery patients in the TRIBE-AKI (Translational Research Investigating Biomarker Endpoints for Acute Kidney Injury) Consortium.PredictorChanges in serum creatinine and cystatin C levels.OutcomePostsurgical incidence of AKI.MeasurementsSerum creatinine and cystatin C were measured at the preoperative visit and daily on postoperative days 1-5. To allow comparisons between changes in creatinine and cystatin C levels, AKI end points were defined by the relative increases in each marker from baseline (25%, 50%, and 100%) and the incidence of AKI was compared based on each marker. Secondary aims were to compare clinical outcomes among patients defined as having AKI by cystatin C and/or creatinine levels.ResultsOverall, serum creatinine level detected more cases of AKI than cystatin C level: 35% developed a ≥25% increase in serum creatinine level, whereas only 23% had a ≥25% increase in cystatin C level (P < 0.001). Creatinine level also had higher proportions meeting the 50% (14% and 8%; P < 0.001) and 100% (4% and 2%; P = 0.005) thresholds for AKI diagnosis. Clinical outcomes generally were not statistically different for AKI cases detected by creatinine or cystatin C level. However, for each AKI threshold, patients with AKI confirmed by both markers had a significantly higher risk of the combined mortality/dialysis outcome compared with patients with AKI detected by creatinine level alone (P = 0.002).LimitationsThere were few adverse clinical outcomes, limiting our ability to detect differences in outcomes between subgroups of patients based on their definitions of AKI.ConclusionsIn this large multicenter study, we found that cystatin C level was less sensitive for AKI detection than creatinine level. However, confirmation by cystatin C level appeared to identify a subset of patients with AKI with a substantially higher risk of adverse outcomes.

Dataset Information

Serum Creatinine Back-Estimation in Cardiac Surgery Patients: Misclassification of AKI Using Existing Formulae and a Data-Driven Model.

Publications

Serum Creatinine Back-Estimation in Cardiac Surgery Patients: Misclassification of AKI Using Existing Formulae and a Data-Driven Model.

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