The role of novel biomarkers in childhood idiopathic nephrotic syndrome: a narrative review of published evidence

Two histological subtypes of idiopathic nephrotic syndrome are commonly recognized in children, namely minimal change nephropathy and focal segmental glomerulosclerosis. Children with minimal change nephropathy (the majority of whom are steroid-sensitive) and focal segmental glomerulosclerosis (the majority of whom are steroid-resistant) require early identification in order to ensure appropriate therapeutic intervention and better outcome. Although renal biopsy and histology remain the ideal diagnostic steps to identify these histological subtypes, reports indicate that serum and urinary biomarkers are now being utilized in the investigation of childhood idiopathic nephrotic syndrome. This paper aims to review the diagnostic and prognostic utility of novel biomarkers in childhood idiopathic nephrotic syndrome and to highlight their role in differentiating steroid-sensitive nephrotic syndrome (SRNS) from steroid-resistant nephrotic syndrome (SSNS). Using the terms "idiopathic nephrotic syndrome," "children," and "biomarkers" the PubMed database was searched for relevant studies related to the topic. Biomarkers such as adiponectin, neopterin, β2-microglobulin, and N-acetyl-β-D glucosaminidase were reported as diagnostic markers. In addition to neopterin and N-acetyl-β-D glucosaminidase, urine vitamin D-binding protein and α1β-glycoprotein were shown to differentiate SRNS from SSNS while N-acetyl-β-D glucosaminidase and β2-microglobulin could predict steroid responsiveness and renal outcome in SRNS. Although progress has been made in demonstrating the diagnostic and prognostic utility of these biomarkers, their limited availability in most laboratories has precluded a complete paradigm shift from the conventional renal biopsy. Nevertheless, further longitudinal studies are required to establish their usefulness as noninvasive predictors of disease response to immunosuppressive therapy.