The authors reply.

Abstract

We appreciate the letter by Kitao et al.1.Kitao T. Kimata T. Kanda E. et al.Soluble urokinase receptor in a toddler with focal segmental glomerulosclerosis.Kidney Int. 2014; 86: 208Abstract Full Text Full Text PDF PubMed Scopus (4) Google Scholar on their case of a 2-year-old boy with focal segmental glomerulosclerosis (FSGS). They reported in their letter that the boy’s serum levels of soluble urokinase receptor (suPAR) during nephrotic stage were not significantly different from those during remission stage. In our study,2.Wada T. Nangaku M. Maruyama S. et al.A multicenter cross-sectional study of circulating soluble urokinase receptor in Japanese patients with glomerular disease.Kidney Int. 2014; 85: 641-648Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar we did not include children or perform serial measurement; however, their results support our data that demonstrated the similar levels of suPAR between the groups of nephrotic and non-nephrotic patients. We also described that the suPAR levels did not correlate with the urinary protein excretion. Shinha et al.3.Shinha A. Bajpai J. Saini S. et al.Serum-soluble urokinase receptor levels do not distinguish focal segmental glomerulosclerosis from other causes of nephrotic syndrome in children.Kidney Int. 2014; 85: 649-658Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar performed a prospective study in a large cohort of Indian children and reported that serum suPAR levels were similar among patients with steroid-resistant nephrotic syndrome in remission, non-nephrotic-range proteinuria, and nephrotic-range proteinuria. They also showed that the suPAR levels did not correlate with urinary protein excretion in their overall patient cohort. Furthermore, in a cross-sectional single-center study to determine the association of serum suPAR levels in children with FSGS or other kidney diseases, Bock et al.4.Bock M.E. Price H.E. Gallon L. et al.Serum soluble urokinase-type plasminogen activator receptor levels and idiopathic FSGS in children: a single-center report.Clin J Am Soc Nephrol. 2013; 8: 1304-1311Crossref PubMed Scopus (77) Google Scholar described that patients with nephrotic-range proteinuria, independently of diagnosis, did not have significantly higher suPAR levels than patients without proteinuria. They also demonstrated that the degree of proteinuria did not correlate with suPAR levels in the overall patient cohort or in the FSGS patient cohort alone. Taken together, even in cohorts of children, serum suPAR level is not a vital marker of disease activity for proteinuric glomerular diseases.