Role of lean body mass for estimation of glomerular filtration rate in patients with chronic kidney disease with various body mass indices.

OBJECTIVE

Glomerular filtration rate (GFR) is the main tool used to diagnose, treat and follow up renal diseases. Age, gender, ethnicity and obesity all affect the relationship between serum creatinine, muscle mass/body weight and GFR. This study aimed to investigate the role of lean body mass for GFR estimation in patients with chronic kidney disease (CKD) with various body mass indices.

MATERIAL AND METHODS

In total, 110 Caucasian adult subjects with CKD referred for GFR measurement by (99m)Tc-DTPA renography were enrolled in the study. The patients were categorized according to body mass index values: <18.5 kg/m(2) (underweight), 18.5-24.9 kg/m(2) (normal), 25-29.9 kg/m(2) (overweight) and >30 kg/m(2) (obese). Lean body mass (LBM) and fat mass were measured by leg-to-leg bioimpedance. Predictive factors were identified by linear regression analysis in each group.

RESULTS

GFR measured by DTPA, creatinine clearance, Cockcroft and Gault, and Modification of Diet in Renal Disease (four-variable) equations was 37+/-27, 42+/-30, 42+/-27, and 49+/-35 ml/min/1.73 m(2), respectively. The predictive role of 1/SCr, age, serum albumin, amount of proteinuria, LBM and fat mass was investigated all groups. None of the factors was significant in underweight and healthy weight groups except for 1/serum creatinine (SCr). LBM/SCr was an independent predictive factor for both overweight and obese groups. 1/SCr accounted for 96.2% of the variability in measured GFR for underweight subjects but only 58.1% of the variability in GFR of obese subjects.

CONCLUSIONS

The formulae derived from SCr should be used cautiously in overweight and obese subjects. LBM measured by bioimpedance was an independent predictive factor of GFR in obese/overweight subjects and added clinically important diagnostic value to 1/SCr. It needs to be investigated as a parameter in further studies attempting to develop formulae for estimating GFR in larger obese and overweight populations.