Images of urine sediments for external quality assessment. (A) CUI-18-05 red blood cell cast (original magnification×400). (B) CUI-18-06 bilirubin crystal (original magnification×100). (C) CUI-18-07 white blood cells (original magnification×200). (D) CUI-18-08 renal tubular epithelial cells (original magnification×400).