XDH and chronic kidney disease: Three recent large trials in CKD (CKD-FIX [Controlled trial of slowing of Kidney Disease progression From the Inhibition of Xanthine oxidase], CREDENCE [Evaluation of the Effects of Canagliflozin on Renal and Cardiovascular Outcomes in Participants With Diabetic Nephropathy] and SONAR [Study Of Diabetic Nephropathy With Atrasentan] have reported and measured kidney function in different ways [14–16].