Supplementation, optimal status, and analytical determination of vitamin D: Where are we standing in 2012?

There is a growing interest for vitamin D in the medical and scientific community as well as in the public medias as illustrated by a huge number of publications. Most experts claim that vitamin D deficiency/insufficiency is widespread with potential important public health consequences. It may seem surprising for many persons that a deficiency in a vitamin may be so frequent in countries where food is so diversified and easily available. In fact, vitamin D is not a vitamin stricto sensu as it is mainly synthesized in the skin under the action of UVB rays, while its food sources are scarce. Furthermore, UVB rays are absent during a marked part of the year at latitudes greater than 35-40°, while pollution and cloud cover reduce the number of UVB reaching the earth, and many factors such as age, skin pigmentation, covering clothes, sun creams reduce the capacity of the skin to synthesize vitamin D3. Vitamin D must be hydroxylated to form 1,25dihydroxyvitamin D (1,25OH2D), the active metabolite. As 1,25OH2D is released into the bloodstream and binds to a receptor present in several distant tissues, it may be considered as a hormone, vitamin D being thus a pre-prohormone. In the present article, we review briefly the metabolism and various effects of vitamin D as well as the vitamin D assays and vitamin D treatments. We define vitamin D deficiency/insufficiency considerin

Serum Creatinine: Not So Simple!

peer reviewedMeasuring serum creatinine is cheap and commonly done in daily practice. However, interpretation of serum creatinine results is not always easy. In this review, we will briefly remind the physiological limitations of serum creatinine due notably to its tubular secretion and the influence of muscular mass or protein intake on its concentration. We mainly focus on the analytical limitations of serum creatinine, insisting on important concept such as reference intervals, standardization (and IDMS traceability), analytical interferences, analytical coefficient of variation (CV), biological CV and critical difference. Because the relationship between serum creatinine and glomerular filtration rate is hyperbolic, all these CVs will impact not only the precision of serum creatinine but still more the precision of different creatinine-based equations, especially in low or normal-low creatinine levels (or high or normal-high glomerular filtration rate range)

Unexpected high levels of Cobalamin (Vitamin B12): Numerous interferences are decreased by PEG treatment.

Cobalamin (Vitamin B12) deficiency is a common cause of anemia. High levels of serum cobalamin is mainly due to cobalamin supplementation. It has also been associated with hematological malignancies, liver or renal diseases. Cobalamin is sometimes found elevated in autoimmune disorders and infectious diseases but concerns are raised on the fact that those serum increases might be due to interference with immunoassays. Those data’s shed the lights on the high prevalence of interference in patients with unexpected high cobalamin level. Precipitation with PEG appears to be an easy and costless method to increase the reliability of cobalamin dosage. In accordance with our results, we recommand to treat systematically every serum with a cobalamin >1500 ng/L

Low prevalence of chronic kidney disease in Far-East Asian populations: impact of the ethnicity factor?

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