How do clinical and psychological variables relate to quality of life in end-stage renal disease? Validating a proximal-distal model

The aims of this study were to: (1) validate the proximal-distal (PD) model in predialysis and early dialysis and (2) examine the role of hemoglobin on quality of life (QoL) in these patient groups. Cross-sectional observational studies of 475 participants recruited from four major university teaching hospitals were conducted. The multi-sample structural equation modeling with latent composite techniques was employed to test the PD model. Seven factors were measured, including QoL, positive affect, depression, physical functioning, kidney disease symptoms, comorbidity and hemoglobin. The results showed that both the equality-constrained and equality-unconstrained PD models were supported by fit statistics. The chi square difference test of the two models was non-significant, indicating that the PD model was consistent across groups. The alternative models were rejected by fit statistics, suggesting that hemoglobin does not impact on psychological states but QoL. This study validates the PD model across the end-stage renal disease (ESRD) patient groups and shows a hierarchical causal relationship between clinical factors, physical functioning, psychological states and QoL, with hemoglobin as an exception. This model provides an empirical framework for integrating and studying a range of clinical factors and health outcomes in ESRD.