As compared to the other stages, evidence for PVAN was associated with a significant decrease of the ratio due to a disproportionately strong increase of urine CXCL‐10 levels (median change of the blood/urine ratio: −0.89, 95% CI: −7.38 to −0.69, P = 0.0042). This evidence concerns the gene CXCL10 and BK-virus nephropathy.