*Review* **Contribution of Predictive and Prognostic Biomarkers to Clinical Research on Chronic Kidney Disease**

**Michele Provenzano 1,\*, Salvatore Rotundo 2, Paolo Chiodini 3, Ida Gagliardi 1, Ashour Michael 1, Elvira Angotti 4, Silvio Borrelli 5, Ra**ff**aele Serra 6, Daniela Foti 2, Giovambattista De Sarro <sup>7</sup> and Michele Andreucci 1,\***


Received: 29 June 2020; Accepted: 12 August 2020; Published: 14 August 2020

**Abstract:** Chronic kidney disease (CKD), defined as the presence of albuminuria and/or reduction in estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2, is considered a growing public health problem, with its prevalence and incidence having almost doubled in the past three decades. The implementation of novel biomarkers in clinical practice is crucial, since it could allow earlier diagnosis and lead to an improvement in CKD outcomes. Nevertheless, a clear guidance on how to develop biomarkers in the setting of CKD is not yet available. The aim of this review is to report the framework for implementing biomarkers in observational and intervention studies. Biomarkers are classified as either prognostic or predictive; the first type is used to identify the likelihood of a patient to develop an endpoint regardless of treatment, whereas the second type is used to determine whether the patient is likely to benefit from a specific treatment. Many single assays and complex biomarkers were shown to improve the prediction of cardiovascular and kidney outcomes in CKD patients on top of the traditional risk factors. Biomarkers were also shown to improve clinical trial designs. Understanding the correct ways to validate and implement novel biomarkers in CKD will help to mitigate the global burden of CKD and to improve the individual prognosis of these high-risk patients.

**Keywords:** end-stage kidney disease (ESKD); cardiovascular disease; epidemiology; CKD; biomarkers
