*4.5. Measurement of s-Uromodulin*

S-Uromodulin was assessed in 20 controls and in 100 KTRs. All serum samples were stored at –80 ◦C before measurements were performed. Measurements of s-Uromodulin were performed using commercial ELISA (Euroimmun, Medizinische Labordiagnostika AG, Lübeck, Germany), as described previously, based on the manufacturer's instructions [5]. Characteristics of the ELISA were as follows, given by the manufacturer: detection limit for plasma samples 2 ng/mL; mean linearity recovery 97% (83–107% at 59–397 ng/mL); intra-assay precision 1.8–3.2% (at 30–214 ng/mL); inter-assay precision 6.6–7.8% (at 35–228 ng/mL); and inter-lot precision 7.2–10.1% (at 37–227 ng/mL). Data analysis was performed using the program Analysis Software Gen5 (Gen5 2.09, BioTek).
