Association of Serum Phosphorus with Hemoglobin Level and its Longitudinal Variation in Patients with Chronic Kidney Disease

Background: Anemia is a common complication of chronic kidney disease (CKD). Hemoglobin variability is a well-documented parameter representing hemoglobin control. However, there is still lack of evidence about whether risk factors related to hemoglobin (Hb) level simultaneously affect Hb variability. This study aimed to evaluate the association of serum phosphorus with hemoglobin level and its longitudinal variation in patients with chronic kidney disease. Methods: Data were obtained from the Chinese Cohort Study of Chronic Kidney Disease (C-STRIDE), which was a nation-wide multicenter prospective cohort study. The association of phosphorus with hemoglobin level was evaluated in 3227 patients. Longitudinal variation of hemoglobin level was evaluated in 753 patients. Linear regression models and logistic regression mod-els were used to assess the association of phosphorus with hemoglobin level, anemia prevalence, and longitudinal variation of hemoglobin over 2 years. Results: Serum phosphorus was negatively associated with hemoglobin level. While 1 mmol/L increase in serum phosphorus was associated with 11.72 g/dL decrease in hemoglobin (95% Confidence interval 14.42 to 9.02 g/dL). Each 0.1 mmol/L increase in phosphorous was associated with 14% increase in prevalence of anemia (odds ratio (OR): 1.14, 95% CI: 1.12 to 1.16). In the longitudinal analysis, serum phosphorus was independently associated with the residual standard deviation and absolute range of hemoglobin. Conclusion: Serum phosphorus level was independently associated with baseline hemoglobin level, the prevalence of anemia and longitudinal variation of hemoglobin in Chinese patients with chronic kidney disease (CKD). Clinical Trial Registration: NCT03041987, available at: https://clinicaltrials.gov/.