Vitamin D measurement and effect on outcome in a cohort of patients with heart failure

Objectives: The aims of this paper were to evaluate the levels of Vitamin D (VitD) in patients with Heart Failure (HF), compared to a control group, to assess the effects of VitD on HF outcome and to compare VitD measurement between LIAISON immunoassay and HPLC-MS-MS methods in this population. Design & Methods: We collected clinical, biochemical and outcome data from 247 patients with HF and in a subgroup of 151 patients, we measured VitD both with LIAISON and HPLC-MS-MS. Results: HF patients had statistically lower 25OHD levels (45.2±23.7 nmol/l vs 58.2±24.0 nmol/l, p<0.001) and a statistically higher prevalence of VitD insufficiency (61.1% vs 39.5%, p<0.001) and deficiency (24.7% vs 6.6%, p<0.001), compared to healthy controls. There was a significant inverse relationship between baseline 25OHD and risk of HF related death, with a HR of 0.59 (95% CI 0.37-0.92, p=0.02), confirmed in a multivariate adjusted analysis. Kaplan-Meier survival analyses showed that VitD insufficiency was associated with reduced survival in HF patients (log rank p=0.017). There was a good agreement between LIAISON and HPLC-MS-MS (Cohen's kappa coefficient 0.70), but the prevalence of VitD insufficiency was significantly higher with the former compared to the latter method (58.3%, n=88 vs 55.6%, n=84, p<0.001). LIAISON underestimated the 25OHD levels and showed a mean relative bias of -0.739% with 95% of limits of agreement (-9.00 to +7.52%), when compared to HPLC-MS-MS. Conclusions: 25OHD levels adequately measured by HPLC-MS-MS, showed to be low in HF population and to be correlated with HF-related risk of death.