Background: Inflammatory markers vary considerably over time in haemodialysis (HD) patients, yet the variability is poorly defined. The aim of the study was to assess changes of plasma levels of pentraxin-3 (PTX-3), C-reactive protein (CRP), albumin and homocysteine (Hcy) over 3 months and the association between the changes in these biomarkers and mortality.
Methods: In 188 prevalent HD patients, inflammatory markers were measured at inclusion and after 3 months. Mortality was recorded during a median follow-up of 41 months. The changes of the biomarker levels were categorized according to change in tertile for the specific biomarker. The variation was calculated as the intra-class correlation (ICC). Mortality was analysed by Kaplan-Meier and Cox proportional hazards model. The predictive strength was calculated for single measurements and for the variation of each inflammatory marker.
Results: The intra-individual variation (low ICC) was largest for PTX-3 [ICC 0.44; 95% confidence interval (CI): 0.33-0.55], albumin (ICC 0.58; 95% CI: 0.49-0.67) and CRP (ICC 0.59; 95% CI: 0.51-0.68) and lowest for Hcy (ICC 0.81; 95% CI: 0.77-0.86). During follow-up, 88 patients died.
Conclusions: PTX-3 measurements are less stable and show higher variation within patients than CRP, albumin and Hcy. Persistently elevated PTX-3 levels are associated with high mortality. Moreover, in multivariate logistic regression we found that stable high PTX-3 adds to the mortality risk, even after inclusion of clinical factors and the three other biomarkers. The associations of decreasing albumin levels as well as low Hcy levels with worse outcome reflect protein-energy wasting.
Keywords: HD; end-stage renal disease; inflammation; pentraxin 3; variation.