CD4 and immune system disorder: Patients with stages 4-5 CKD had a median age of 38 (25th-75th percentile, 33-45) years, were predominantly male (69%) and of black ethnicity (54%), had low rates of hepatitis B or C coinfection (9% and 4%, respectively), and had more advanced immunodeficiency at baseline (median CD4 cell count, 213 [25th-75th percentile, 93-365] cells/μL compared with 348 [25th-75th percentile, 203-520] cells/μL in those not categorized as CKD stages 4-5).