Nat. Rev. Nephrol. 10, 77–87 (2014); doi:10.1038/nrneph.2013.251

In the February 2014 issue of Nature Reviews Nephrology, the key in Figure 4 of this article was labelled incorrectly. The correct labelling is as follows: pale green <1; dark green 1–2, blue 2–3; purple >3.5. This error has been corrected online.