Soluble urokinase-type plasminogen activator receptor as a biomarker for focal segmental glomerulosclerosis; a retrospective analysis

Abstract

Background: Focal segmental glomerulosclerosis (FSGS) is a clinicopathological syndrome that presents with proteinuria, usually in the nephrotic range and evidence of histologic lesions of focal and segmental glomerular sclerosis with diffuse foot-process effacement. Recently, suPAR (soluble urokinase-type plasminogen activator receptor) was proposed as the potential circulating causative factor for primary FSGS. Objectives: We performed a cross-sectional study with the aim to determine whether there is a relationship between suPAR serum levels and primary FSGS. The secondary aim was to associate serum suPAR levels with kidney dysfunction. Patients and Methods: We enrolled a total of 90 patients with both suPAR serum levels and proteinuria. From these, 61 patients performed a renal biopsy. Results: The mean age was 49.8±17.2 years, 37 was females (60.7%) and 54 were Caucasian race (91.5%). FSGS was diagnosed in 30 patients (49%). suPAR levels were positive in 34 patients (55.7%) and negative in 27 (44.3%). Concerning the positive results, 17 patients had the histologic diagnosis of FSGS, which gives the test a sensibility of 28%. Concerning the negative results, 14 patients had a different histologic diagnosis other than FSGS, which gives the test a specificity of 23%. The predicted positive value was 50% and the predicted negative value was 52%. suPAR serum levels were not correlated with 24 hours proteinuria (P=0.5), but we found a positive correlation with C-reactive protein (P=0.037) and an inverse correlation with estimated glomerular filtration rate (eGFR) (P<0.001). Conclusions: We found that a positive suPAR test is not a marker of FSGS, but it can be a marker of podocyte and glomerular lesion, as it is inversely correlated with renal function in a cohort of proteinuric patients. Further studies are needed to further validate suPAR as a specific biomarker of glomerular damage.