**8. Conclusions**

In summary, tubular stress test assessment using the FST is a rediscovered and promising new tool to stratify risk in different kidney diseases. Multi-center, prospective studies with large enough sample sizes, applying standardized furosemide dosage and timing and comparing the FST to other novel plasma and urinary biomarkers are necessary to adequately validate results and define the possible clinical applications of the test.

**Supplementary Materials:** Supplementary materials can be found at http://www.mdpi.com/1422-0067/21/9/3086/ s1.

**Author Contributions:** Development of the idea: A.C. and J.B.-M. Writing—Review and Editing: C.A., J.R.S. and A.L.V. Supervision: A.C., E.B.-M. and J.B.-M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.
