SPP1 and urolithiasis: To determine whether the uFL-OPN had a poly-N-acetyllactosamine structure (polyLacNAc) or not, and whether its level of stone forming urolithiasis patients was significantly increased or not, we performed immunoblotting and Lycopersicon esculentum lectin (LEL) blotting analysis by using immunoprecipitated OPN from HVs and stone forming patients.