Clinical and experimental evidence suggests the pathogenic role of circulating permeability factors, including soluble urokinase plasminogen activating receptor (suPAR). Serum suPAR levels were found to be elevated in Caucasian adults with primary FSGS and in two cohorts of children with FSGS from Europe and the United States.
This new study in KI March 2014 issue from India looked at the role of suPAR in all children with nephrotic syndrome. Compared to controls, suPAR levels were highest in FSGS and then other nephrotic syndromes from MCD and other congenital diseases. Interestingly, the study failed to show that this circulating factor that was really hallmark of FSGS diagnosis was specific for FSGS. Rather, it might be a biomarker for nephrotic syndrome in general. Interestingly, levels of suPAR significantly correlated inversely with eGFR and CRP.
So what this study is telling us is that suPAR gets elevated with downtrending GFR- perhaps it’s just a renal clearance marker. In addition, suPAR has been found to be elevated in sepsis, malaria and chronic infections such as Hepatitis and HIV. So it’s unclear if suPAR really is a marker of podocyte injury but rather a marker of generalized inflammation.
So, suPAR doesn’t answer our question for FSGS permeability factor anymore. This study really highlighted the non specificity of suPAR for FSGS and even perhaps podocyte injury.