Association Between Whole Blood Rubidium Levels and Anemia in Maintenance Hemodialysis Patients: A Multicenter Cross-Sectional Study.

Anemia represents a common and clinically significant complication among maintenance hemodialysis (MHD) patients. Rubidium (Rb), which shares biochemical properties with potassium and enters cells through Na⁺/K⁺-ATPase, potentially influences erythrocyte function; however, its relationship with anemia in MHD populations has not been explored. This multicenter cross-sectional investigation enrolled 679 MHD patients from three hospitals in China during September to December 2021. Whole blood Rb concentrations were quantified using inductively coupled plasma mass spectrometry (ICP-MS). Anemia was defined as hemoglobin (Hb) below 11.0 g/dL. The association was evaluated through restricted cubic spline (RCS) analysis, multivariable logistic regression, and linear regression models. Anemia prevalence reached 55.23% in the study population. RCS analysis revealed an approximately linear inverse relationship between ln-transformed Rb and anemia risk (P for nonlinearity = 0.069, P overall < 0.001). Following adjustment for demographic factors, comorbidities, dialysis adequacy, nutritional markers, inflammatory indicators, iron metabolism parameters, and erythropoiesis-stimulating agent usage, each 1 mg/L elevation in Rb corresponded to 77% reduced odds of anemia (OR = 0.23, 95%CI: 0.11-0.39). Patients in the highest Rb quartile exhibited 70% lower anemia risk compared to those in the lowest quartile (OR = 0.30, 95%CI: 0.18-0.51; P for trend < 0.001). Each 1 mg/L Rb increment was associated with 1.471 g/dL higher Hb concentration (β = 1.471, 95%CI: 1.110-1.833). These associations persisted across all examined subgroups. Our findings indicate that elevated whole blood Rb levels independently correlate with reduced anemia prevalence and higher Hb concentrations in MHD patients, positioning Rb as a candidate biomarker for anemia risk stratification in this population.