FGF23 and systemic lupus erythematosus: However, a study of 60 patients with SLE found no significant difference in plasma FGF-23 levels between patients with renal involvement and those without (106.49 ± 88.2 vs. 93.84 ± 74.67 pg/mL, p = 0.56), and similar plasma FGF-23 levels were noted in SLE patients and healthy controls (99.6 ± 79.86 vs. 139 ± 12.3 pg/mL, p > 0.05).