Diagnostic and prognostic biomarkers for tubulointerstitial fibrosis

Renal fibrosis is the final common pathophysiological pathway in chronic kidney disease (CKD) regardless of the underlying cause of kidney injury. Tubulointerstitial fibrosis (TIF) is considered to be the key pathological predictor of CKD progression. Currently, the gold‐standard tool to identify TIF is kidney biopsy, an invasive method that carries risks. Non‐invasive diagnostics rely on an estimation of glomerular filtration rate and albuminuria to assess kidney function, but these fail to diagnose early CKD accurately or to predict progressive decline in kidney function. In this review, we summarize the current and emerging molecular biomarkers that have been studied in various clinical settings and in animal models of kidney disease and that are correlated with the degree of TIF. We examine the potential of these biomarkers to diagnose TIF non‐invasively and to predict disease progression. We also examine the potential of new technologies and non‐invasive diagnostic approaches in assessing TIF. Limitations of current and potential biomarkers are discussed and knowledge gaps identified. figure legend The best predictor of chronic kidney disease is tubulointerstitial fibrosis (TIF). Kidney biopsy is the gold‐standard diagnostic method for TIF, which is invasive. Non‐invasive methods might involve assessment of kidney function, identification of potential urinary and blood biomarkers and the use of new technologies. Assessment of kidney function by measuring glomerular filtration rate and albuminuria has poor diagnostic and prognostic accuracy for TIF. In this review, we present current and potential soluble biomarkers and new technologies and discuss their diagnostic and prognostic accuracies.