Vitamin D, anemia, and fibroblast growth factor 23: Ethnic disparities in Algerian chronic kidney disease patients

This study investigates ethnic differences in vitamin D levels and bone-related biomarkers among Algerian CKD patients, focusing on the interactions between vitamin D, anemia, and FGF23. A multicenter, cross-sectional study involved 284 CKD patients in stages 3 and 4, with a mean age of 54±1.17 years. Participants were recruited from nephrology units in three distinct geographic regions of Algeria: Algiers (Mediterranean), Ghardaïa (sub-Saharan), and Tamanrasset (Saharan). Biochemical analyses included serum levels of 25OH vitamin D, iPTH, iFGF23, calcium, phosphorus, and hemoglobin. Multiple logistic regression was used to assess the association between anemia and vitamin D levels. Linear regression analysis identified predictors of iFGF23 in hemoglobin levels. A two-way ANOVA was performed to examine the influence of vitamin D levels across different ethnic groups. Patients from Tamanrasset exhibited significantly lower levels of 25OH vitamin D and hemoglobin, and higher levels of phosphorus, iFGF23, and iPTH, compared to those from Ghardaïa and Algiers. Anemia was independently associated with lower serum 25OH vitamin D concentrations (β=-0.11, P=0.001), while iFGF23 levels were inversely associated with hemoglobin levels (β=-3.3, P=0.01). A significant interaction between anemia and vitamin D status was observed among Black patients (P=0.0001), but not among white patients (P=0.7). These findings underscore notable ethnic disparities in vitamin D status and mineral biomarkers among Algerian CKD patients. The interplay between vitamin D, anemia, and FGF23 highlights the need for ethnically tailored care, particularly for patients in the Saharan region of Tamanrasset.