Serum phosphate levels associated with anemia in non-dialysis patients with chronic kidney disease

Over the past decade Chronic kidney disease (CKD) and mineral and bone disorder (MBD) and renal anemia are important factors in patients with CKD, only few studies have analyzed the relationship between them not much is known.

Anemia in patients with CKD, known as “renal anemia,” is caused by erythropoietin (EPO) deficiency, and current treatment strategies are mainly focused on this condition. Anemia has become a common complication of (CKD) and an established risk factor for congestive heart failure and cardiovascular disease (CVD).

A retrospective cross sectional study in BMC Nephrolgy evaluated the relationship between CKD-MBD and anemia in patients with CKD who did not receive erythropoiesis-stimulating agent or iron therapies. The study found that there was an association between high serum phosphate levels and low Hb levels in patients with CKD not receiving treatment for anemia. These results highlight the possibility of a mechanistic overlap between CKD-MBD and anemia.

This retrospective cross-sectional study included patients with CKD aged ≥ 20 years with estimated glomerular filtration rate (eGFR) categories G2a to G5 who were referred to the Fuji City General Hospital between April 2018 and July 2019. The exclusion criterion was ongoing treatment for CKD-MBD and/or anemia.

The key findings of the study are

• The data of 300 patients with CKD were analyzed in this study. The median age of patients was 71 (range, 56.5–79) years.

• The median eGFR was 34 (range, 20–48) mL/min/1.73 m2, and the mean hemoglobin (Hb) level was 12.7 g/dL (standard deviation, 2.3), which decreased as the CKD stage increased.

• In a multivariate linear regression analysis of anemia-related factors, including age, renal function (eGFR), nutritional status, inflammation, and iron dynamics (serum iron level, total iron-binding capacity, ferritin levels), the serum phosphate levels were significantly associated with the Hb levels ( P < 0.001).

• Subgroup analysis revealed a robust association between serum phosphate levels and Hb levels in the low-ferritin ( -0.94 [-1.53, -0.35]; P = 0.002) and advanced CKD groups (-0.89 [-1.37, -0.41]; P < 0.001).

Researchers concluded that “We found an association between high serum phosphate levels and low Hb levels in patients with CKD not receiving treatment for anemia. These results underscore the possibility of a mechanistic overlap between CKD-MBD and anemia.”

Reference: Kato, K., Nakashima, A., Ohkido, I. et al. Association between serum phosphate levels and anemia in non-dialysis patients with chronic kidney disease: a retrospective cross-sectional study from the Fuji City CKD Network. BMC Nephrol 24, 244 (2023). https://doi.org/10.1186/s12882-023-03298-9.