Biological variation of metabolic cardiovascular risk factors in haemodialysis patients and healthy individuals

BACKGROUND: Maintenance haemodialysis (HD) is associated with a very high cardiovascular risk and the assessment of metabolic cardiovascular risk factors is essential for an adequate diagnosis and management. The aim of the study has been to estimate the biological variation (BV) of serum lipids, calcium, inorganic phosphorus, 25-OH vitamin D, C-reactive protein and plasma intact parathyroid hormone (PTHi) and total homocysteine, to evaluate whether HD alter the homeostatic set-point of these magnitudes. METHODS: Blood samples were collected from 18 HD patients in steady-state conditions, one per month during 6 months, and from 11 healthy volunteers at weekly intervals over 5 weeks. BV data were derived using CV-ANOVA. RESULTS: Within-subject coefficients of variation (CVI) and derived reference change values (RCV) estimated in HD patients were significantly higher than in healthy individuals for calcium (CVI =3.8% vs. 2.3%) (RCV =12.6% vs. 7.6%), inorganic phosphorus (13.1% vs. 8.0%) (RCV =38.7% vs. 30.1%) and PTHi (20.3% vs. 11.3%) (RCV =57.5% vs. 34.0%). CONCLUSIONS: For calcium, inorganic phosphorus and PTHi, RCV derived from advanced disease-specific BV data is recommended for the management of bone-mineral disturbances in HD patients. For the rest of cardiovascular risk factors, the use of RCV derived from healthy individuals could be appropriate.