FP322THE ASSOCIATION OF SERUM CREATININE VARIABILITY AND PROGRESSION TO CKD

Abstract

Introduction and Aims: Pre-dialysis patients demonstrate high serum creatinine (SC) variability and increased acute kidney injury (AKI) hospitalizations (AJKD 2012;59:513). SC variability also associates with high death rates (KI 2012; 82:1208). We examined the association between high SC variability and progression of CKD in a large cohort of US veterans with estimated glomerular filtration rates (eGFR) > 30 ml/min/1.73 m2. Methods: Patients admitted for any cause between 10/1/1999 and 12/31/2005 with at least 4 months with SC readings and initial eGFR > 30 ml/min/1.73 m2 were selected from the VA database. eGFR calculation used CKD-EPI formula. An autoregression-based slope was computed for each patient using monthly peak SC. To ensure that slope and variability were mathematically independent, SC variability was computed as the root mean-square residual of peak monthly SC readings from the regression line. CKD4-date was the first date when eGFR permanently fell below 30 ml/min/1.73 m2. Logistic regression was used to test prediction models for CKD4 using as predictors: initial eGFR, SC variability, SC slope, age, race, sex, number of months with SC readings, and comorbidities (DM, CAD, PNE, MI, angina, AKI, COPD, CHF). For subjects with an admission for PNA, CAD, CVA, MI, or CHF, survival analysis was used to examine time from first admission to entry into CKD4, stratified by SC variability quartile. Time-to-event analysis was also used (Kaplan-Meier [KM] and Cox regression with the covariates mentioned above). Patients who did not enter CKD4 were censored at death or 12/31/2005, whichever came first. Results: 342,086 patients were used in the logistic regression model predicting entry into CKD4, 36,108 of whom (10.6%) reached CKD4. The logistic model had very strong prediction accuracy (c=.94) with sensitivity and specificity of .86 and .86, respectively. After correcting for all covariates, SC variability was strongly associated with entry into CKD4 (OR 3.79 [3.67-3.91], p