Urine samples were centrifuged (12,000 rpm for 10 min) and stored at −80°C within 12 h after patient enrollment. uNGAL, uIL-18, uKIM-1, and uCysC were measured by the ARCHITECT platform (Abbott Laboratories, Abbott Park, Illinois) (21). These assays used a chemiluminescent microparticle immunoassay using a noncompetitive, 2-antianalyte antibody sandwich. The assays include a microparticle reagent prepared by covalently attaching an antianalyte antibody to paramagnetic particles and a conjugate reagent prepared by labeling a second antianalyte antibody with acridinium. The calibrators for the uNGAL, uIL-18, and uKIM-1 assays were recombinant proteins, and the calibrators for the uCysC assay were prepared from human urine. The highest calibrator for each assay was 1,500 ng/ml, 1 ng/ml, 10 ng/ml, and 2500 ng/ml for uNGAL, uIL-18, uKIM-1, and CysC, respectively. Specimens were diluted to read within the calibration curve. Coefficients of variation were 3.0% for uNGAL at a 385 ng/ml (21), 2.5% for uKIM-1 at 5.8 ng/ml (Abbott Laboratories), 2.2% for uIL-18 at 0.048 pg/ml (Abbott Laboratories), 1.8% for uCysC at 350 ng/ml (Abbott Laboratories), and similar at other cut points. uL-FABP was measured using a sandwich-type enzyme-linked immunosorbent assay kit (CMIC Co., Ltd., Tokyo, Japan). The coefficient of variation was 6.8% for uL-FABP at 13 ng/ml (22). Monomeric uNGAL (23 to 26 kDa) was measured by immunoblots, which were prepared with nonreducing 4% to 15% gradient polyacrylamide gels (Bio-Rad, Hercules, California) using standards (0.3 to 3 ng) of human recombinant NGAL and NGAL antibody (AntibodyShop, Copenhagen, Denmark). The coefficient of variation was <5% at different cut points (16). sCr was assayed at each hospital by the Jaffe reaction, calibrated traceable to isotope dilution mass spectrometry.