Serum levels of soluble urokinase plasminogen activator receptor in Japanese patients with chronic kidney disease.

Abstract

To the Editor: We read with interest the recent article by Wada et al.1 on the role of soluble urokinase plasminogen activator receptor (suPAR) levels in Japanese patients with focal segmental glomerulosclerosis (FSGS) and chronic kidney disease (CKD). They demonstrated that suPAR levels were significantly affected by renal function and were not effective in discriminating FSGS from other glomerular diseases, indicating that suPAR levels are not a potent diagnostic marker for clinical use in Japanese patients. They did not, however, describe the relationship between serum suPAR levels and the progression of renal injury in Japanese CKD patients. Given that the clinical significance of serum suPAR in CKD is unclear, we studied the relationship between serum suPAR and various clinical parameters in 487 Japanese CKD patients. In addition to measuring the basal levels of serum clinical parameters, including suPAR and creatinine (Cr) levels, estimated glomerular filtration rate (eGFR), and urine protein to Cr ratio, we also evaluated serum and urine samples collected after 1 and 2 years (n=208). Similarly, our results show that suPAR levels are inversely correlated with eGFR (P<0.0001, r=−0.275), and positively associated with CKD stage (P<0.0001) and urine protein to Cr ratio (P<0.0001, r=0.157; Figure 1a–c), indicating that renal function significantly affects suPAR levels. Notably, with respect to the relationship between basal suPAR levels and the progression rate of kidney function (ΔeGFR=[final eGFR−initial eGFR]/initial eGFR), suPAR levels were inversely associated with ΔeGFR in samples from year 1 (P<0.0001, r=−0.148; Figure 1d) and year 2 (P=0.0002, r=−0.126; Figure 1e).