Determination of urine KIM-1

We determined the urine concentrations of KIM-1 using an ELISA kit (R&D Systems, Minneapolis, MN, USA & Canada), which is commercially available. We measured the concentrations according to the manufacturer’s instructions, with results in nanograms per millilitre (ng/ml). The limit of detection of KIM-1 levels was 0.07 ng/ml.

We normalised the urine concentrations of NGAL and KIM-1 for urine concentration of creatinine measured by Jaffé’s method (uNGAL-1/cr., uKIM-1/cr.) to account for a potential confounding effect of urine dilution. It was expressed in nanograms per milligram of creatinine (ng/mg cr.). The level of serum creatinine was determined by Jaffe’s method and shown in milligrams per decilitre. We calculated the estimated glomerular filtration rate (GFR) according to Schwartz formula (eGFR = 0.45 × L/Scr., where L is length in centimetres, and Scr. is serum creatinine in milligrams per decilitre).