In the Original Investigation entitled “Non-GFR Determinants of Low-Molecular-Weight Serum Protein Filtration Markers in CKD” that appeared in the December 2016 issue of AJKD,1 there was an error regarding the source of the β-Trace Protein (BTP) and β2-Microglobulin (B2M) samples. The samples were reported as being measured in serum; however, the samples were measured in EDTA plasma.