Markers of kidney function in the elderly in relation to the new CKD-EPI formula for estimation of glomerular filtration rate

INTRODUCTION Neutrophil gelatinase-associated lipocalin (NGAL) has been recently proved useful in the quantitation of chronic kidney disease (CKD). The aim of the study was to assess prevalence of CKD according to the Modification of Diet in Renal Disease (MDRD), Cockcroft-Gault, and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formulae in 412 patients with normal serum creatinine and markers of kidney function/injury such as NGAL, cystatin C, and kidney injury molecule-1 (KIM-1) in these patients in relation to age (below and over 65 years). MATERIAL AND METHODS We included in the study 1005 patients with coronary artery disease and normal serum creatinine. However, markers of kidney function/injury were assessed in 412 patients. The NGAL, cystatin C and KIM-1, were assessed using commercially available kits. RESULTS Patients over 65 years had significantly lower estimated glomerular filtration rate (eGFR) than their younger counterparts despite identical creatinine. They also had significantly lower haematocrit, despite similar Hb, lower platelet count, higher serum fibrinogen, higher systolic (SBP) and lower diastolic blood pressure, higher serum NGAL and cystatin C, but similar urinary NGAL and KIM-1. Serum NGAL correlated with age, haematocrit, leukocyte, platelet and erythrocyte count, eGFR, creatinine, fasting glucose, HbA(1c), fibrinogen, SBP, and diabetes duration. In multiple regression analysis kidney function (eGFR, creatinine clearance or creatinine), cystatin C and SBP were predictors of serum NGAL. CONCLUSIONS In our study we found a very high prevalence of CKD up to 61% in elderly patients with coronary artery disease and normal serum creatinine. Neutrophil gelatinase-associated lipocalin could be a sensitive marker of kidney function, particularly in elderly patients with another risk factor for kidney damage, i.e. hypertension.