Nat. Rev. Nephrol. 9, 337–347 (2013); doi:10.1038/nrneph.2013.74

In the originally published article the values in Box 1 were incorrect. The insufficiency range should have been 50–74 nmol/l and the optimal range should have been 75–100 nmol/l. The errors have been corrected for the HTML and PDF versions of the article.