Association of clinical characteristics with urine uromodulin in children with chronic kidney disease

Background Uromodulin is the most abundant protein in the urine of healthy adults, and higher urine concentrations mark better tubular health. Greater kidney size and function are predictors of higher uromodulin levels in adults. Urine uromodulin has not yet been studied in children with chronic kidney disease (CKD). Thus, we sought to determine the relationship between age and kidney function with urine uromodulin levels in children with CKD. Methods In the CKD in Children (CKiD) cohort, we utilized multivariable linear regression to evaluate the relationship of age and eGFR with urine uromodulin levels. The primary outcome was uromodulin indexed to urine creatinine (Umod/Cr, mg/g), which was log 2 -transformed given its skewed distribution. Results Among 677 CKiD participants, the median age was 11.8 years (8.2–15.3), the median eGFR was 49 ml/min/1.73 m 2 (37–63), the etiology of CKD was glomerular disease in 31%, and the median Umod/Cr level was 0.114 mg/g (0.045–0.226). In the multivariable models, each one-year older age was associated with 0.18 (12%) lower log 2 (Umod/Cr) and 0.20 (13%) lower log 2 (Umod/Cr) among those with non-glomerular and glomerular disease, respectively ( p < 0.001). However, we did not find a statistically significant association between eGFR and Umod/Cr in either participants with non-glomerular or glomerular disease ( p = 0.13 and p = 0.58, respectively). Conclusions Among children with CKD, older age is significantly associated with lower Umod/Cr, independent of eGFR. Further studies are needed to comprehensively evaluate age-specific reference ranges for urine uromodulin and to evaluate the longitudinal relationship of uromodulin with both age and eGFR in children with CKD. Graphical abstract A higher resolution version of the Graphical abstract is available as Supplementary information