LCN2 and stage 5 chronic kidney disease: COPD: chronic obstructive pulmonary disorder; CRF: chronic renal failure; CKD: chronic kidney disease; OR: odds ratio; HR: hazard ratio; eGFR: estimated glomerular filtration rate; ESRD: end-stage renal disease; FEV1: forced expiratory volume in the first second; CKDcys: chronic kidney disease based on cystatine; CKDcr: chronic kidney disease based on creatinine; FVC: forced vital capacity; eGFRcr: eGFR based on creatinine; eGFRcys: eGFR based on cystatine; AFL: airflow limitation; sTNF-R1: soluble tumor necrosis factor receptor 1; NGAL: neutrophil gelatinase-associated lipocalin