Objective: Vitamin D has several functions in cell growth, immunity, and metabolism. Vitamin D deficiency has been associated with rickets. In deficient states, there is a higher risk for autoimmune diseases, cancers, myocardial infarction, diabetes, and infectious diseases. The aim of the present study was to investigate the effect of storage conditions for vitamin D analysis by liquidchromatography tandem mass spectrometry (LC-MS/MS).

Materials and Methods: Blood samples (n=35) were randomly obtained on K2-EDTA containing tubes from the subjects referred to Ankara Numune Training and Education hospital polyclinics. Plasma was obtained by centrifugation and three aliqouts were stored. According to the study design, three different groups were constituted. Group 1 consisted of plasma samples stored at room temperature (n=35), Group 2 consisted of plasma samples stored at 2-8ºC (n=35) and group 3 consisted of plasma samples stored at -80ºC (n=35). Vitamin D analysis was performed by liquid-chromatography tandem mass spectrometry at Ankalab Laboratory on the next day.

Results: Statistical analysis was performed by Wilcoxon test with SPSS v15. Group 3 vitamin D results were significantly higher than both Group 1 and 2 (for both p<0.001). There was no statistically difference between Group 1 and 2 vitamin D results (p=0.051).

Conclusion: According to these results, if the plasma samples are not to be analyzed on the same day, vitamin D analysis by liquid-chromatography tandem mass spectrometry will be more reliable by freezing plasma samples immediately after centrifugation.