#4914 LOW LEAN BODY TISSUE IS AN INDEPENDENT RISK FACTOR FOR KIDNEY DISEASE PROGRESSION AND MORTALITY IN PATIENTS WITH ADVANCED CHRONIC KIDNEY DISEASE
Authors: Roldán Deborah Soledad , Valcarce Eduardo Gallego , Gruss Enrique , Shabaka Amir 
Published: June 2023

Abstract

Background and Aims
Lean tissue mass is a marker of good health and is associated with a lower risk of death in patients without chronic kidney disease (CKD). A potentially underestimated risk factor for impaired renal function is low serum albumin concentration. Previous studies have shown that even small decreases in serum albumin concentration levels are strongly associated with cardiovascular disease, heart failure, impaired kidney function, and mortality in vulnerable populations. An association between low lean body tissue with mortality in patients with stage 4 and 5 CKD has recently been demonstrated. The aim of this study was to evaluate the effect of lean body tissue index (LTI) measured by multifrequency bioelectrical impedance analysis (BIA) on kidney disease progression and mortality in a cohort of patients with stage 4 and 5 CKD.

Method
We performed a retrospective observational cohort study that included patients with stage 4 and 5 CKD who were referred to the Advanced Chronic Kidney Disease outpatient clinic at our centre between January 2014 and December 2020, in whom a baseline measurement of body composition by using BIA was performed in the first 6 months of follow-up. Baseline clinical and laboratory parameters (serum creatinine, glomerular filtration rate, serum albumin, hemoglobin, cholesterol, triglycerides, calcium, phosphorus, PTH and CRP) were defined as those observed at the time of BIA measurement. Low lean tissue was defined as having LTI values below the 10th centile adjusted by age and sex. Renal survival was defined as the absence of need of renal replacement therapy (RRT) at the end of follow-up.

Results
The study included 145 patients who had a mean age of 72 ± 11.8 years, 69.7% were males, with a mean GFR measured by CKD-EPI of 20.4 ± 4.7 ml/min, mean albumin of 4.1 ± 0.3 g/dl and median urine albumin-creatinine ratio (uACR)of 413 mg/g (IQR 98-1341). The mean body mass index of the population was 30.1 ± 6.1 kg/m2, and BIA showed a mean LTI of 15.4 ± 3.9 kg/m2 and fat tissue index (FTI) of 14.1 ± 6.8 kg/m2. Nineteen patients (13.1%) had low LTI. Patients with low LTI were younger (65.9 ± 12.8 vs 73 ± 11.4 years, p = 0.013) and had higher uACR (1444 [484-1815] vs 318 [68-1188] mg/g, p = 0.002) with no differences in sex, GFR, and other laboratory parameters. After a mean follow-up of 27.7 months (IQR 15.3-45.4), 72 (49.7%) showed CKD progression to RRT and 55 patients (37.9%) died. The Kaplan-Meier survival analysis showed that patients with low LTI had a worse renal survival (log-rank 5.5, p = 0.019) and overall survival (log-rank 7.6, p = 0.006). The multivariate Cox regression analysis showed that low LTI (HR 2.28, 95% CI 1.12-4.62), lower GFR (HR 0.86, 95% CI 0.81-0.92) and higher uACR (HR 1.001, CI 95% 1-1.001) were independent risk factors for CKD progression to ESKD, while low LTI (HR 3.16, 95% CI 1.42-7.05), age (HR 1.09, CI 95% 1.05-1.13) and serum albumin (HR 0.31, CI 95% 0.13-0.77) were the factors that were independently associated with mortality.

Conclusion
Low lean body tissue index measured by multifrequency bioelectrical impedance analysis is and independent risk factor for CKD progression and mortality in stage 4-5 CKD. Close monitoring of nutritional status by BIA should be followed in these patients to provide timely and adequate nutritional interventions that might help in improving patient outcomes.