Mendelian randomization study of urate vs renal function does not support conclusions from observational studies Tony Merriman, University of Otago 5 August 2014 The authors did not consider this very relevant article: Hughes et al. Mendelian randomization analysis associates increased serum urate, due to genetic variation in uric acid transporters, with improved renal function. Kidney International 2014;85:344-51. EPub Sep 18 2013. This Mendelian randomization study provides evidence, consistent with the Palmer et al. Mendelian randomization study in urate vs ischaemic heart disease quoted by the authors, that observational studies claiming that urate causes reduced renal function are confounded. The Hughes et al study found no evidence, using genetic variants for increased urate as instruments, that increased urate was causal for reduced renal function. In fact, in males, they found evidence for the opposite - that increased urate was beneficial of renal function. Competing interests I am senior author of the Hughes et al paper mentioned in my comment.