FGF23 and kidney failure: Assessing the predictive value of eGFR for their concentration is furthermore also relevant, because several LMWP’s, such as interleukin-6 (IL-6) [23]–[26], tumor necrosis factor-alpha (TNF-α) [27], [28], beta-2-microglobulin (β2M) [29], [30], and fibroblast growth factor-23 (FGF-23) [31]–[33], have been linked to mortality or surrogate outcomes like vascular damage or progression of kidney failure.