C. A. Fuhrer¹, M. Kaeslin Meyer¹, AR. Huber¹, R. Herklotz¹

¹Center of Laboratory Medicine, Kantonsspital Aarau, Aarau, Switzerland

Undiagnosed vitamin D deficiency, determined as a serum 25-hydroxyvitamin D (25-OH-D) level below cut-off, is common. The fat-soluble vitamin D plays an important role in calcium homeostasis and bone metabolism and in addition seems to decrease the risk of important chronic illnesses such as cancers, infectious and cardiovascular diseases. After a public lecture on vitamin D-deficiency in our hospital, the audience had the opportunity to participate in a study analysing serum 25-OH-D levels. 114 participants (88 women, 26 men; age: 21 – 86 years) enrolled. Serum 25-OH-D levels were measured using HPLC and LC-MS/MS methods. Both methods showed a good correlation concerning 25-OH-D3 (cholecalciferol, vitamin D3) while only the LC-MS/MS method was able to distinguish between 25-OH-D2 (ergocalciferol, vitamin D2) and 25-OH-D3 even though the HPLC method was certified for the analysis of both metabolites. Assuming that a concentration of 75 nmol/l (50 nmol/l) or greater indicates a sufficient vitamin D status, 65.8% (39.5%) of all participants demonstrated a vitamin D deficiency. 60.2% (36.4%) of the women and 84.6% (50.0%) of the men had 25-OH-D3 concentrations below 75 nmol/l (50 nmol/l). The median of all participants was 59.9 nmol/l while women showed higher 25-OH-D3 levels (median 61.9 nmol/l) compared to men (median: 47.6 nmol/l). Correlating the age with 25-OH-D3 levels a moderate difference was found between young and older men (median: 42.3 vs. 54.7 nmol/l) while an additional difference was observed between pre- and postmenopausal women (median: 39.0 vs. 75.1 nmol/l). According to our results we conclude that vitamin D deficiency in the region of Aarau is less present in postmenopausal women during wintertime. Considering that the endogenous 25-OH-D3 production in the elderly is less effective and generally is decreased during wintertime these results are surprising. A possible explanation is an increasing personal interest of the elderly in health care resulting in more outdoor activities and an increased vitamin D supplementation.