Interestingly, the association between venular tortuosity and CKD stages 3–5 was strongest among the 147 participants with poorer renal function for both estimating equations compared to the 351 additional participants identified using the cystatin C equation only (mean eGFRscr: 49.6 [n = 147] versus 75.4 [n = 351] mL/min/1.73m2 and eGFRcys: 45.1 [n = 147] versus 51.5 [n = 351] mL/min/1.73m2; data not shown). This evidence concerns the gene CST3 and chronic kidney disease.