ALB and acute kidney injury: (1) In the AKI group, the levels of hemoglobin, evaluated glomerular filtration rate (eGFR), serum albumin and complement 3 were significantly lower (P<0.05); the proportions of microscopic polyangiitis (MPA) and levels of serum creatinine (SCr) on admission, red blood cell (RBC) counts in urine, 24-hour urine protein excretion (UPE) and Birmingham Vasculitis Activity Score (BVAS) were significantly higher (P<0.05).