Modelling and Prediction of 25-Hydroxyvitamin D Levels in Norwegian Relapsing-Remitting Multiple Sclerosis Patients
Neuroepidemiology , 07/18/2012
Benth JS et al. – The seasonal fluctuations of 25(OH)D levels in Norwegian relapsing–remitting MS patients are subject to pronounced intra– and inter–individual variation. The most representative measurements of 25(OH)D levels are taken in February.Methods
- During December 2004 and July 2008, 762 serum samples were collected from 92 Norwegian relapsing-remitting MS patients.
- Time series analysis and multivariate modelling techniques were used to model seasonal fluctuations and intra- and inter-individual variations in 25(OH)D values.
- Most patients reached their lowest 25(OH)D level in March/April and the highest in July/August.
- There were substantial intra-individual variations in the extent of seasonal fluctuation, with 36.6% of explainable variation in seasonally adjusted 25(OH)D levels (on a logarithmic scale) attributable to the patient level.
- The remaining 63.4% could be accounted for by sources of inter-individual variation.
- Both the total and inter-individual variabilities were lowest in February, and the prediction interval in this month was up to 26% narrower compared to other months.
- The prediction intervals would be at least 21% wider with only one observation available per patient.