Seasonal vitamin D changes and the impact on health risk assessment.

OBJECTIVE: To investigate seasonal variation of vitamin D levels in 148,821 serum samples during a 2year time period in a northern-latitude city in the United States. METHODS: Total vitamin D assay testing by chemiluminescence was performed on the DiaSorin Liaison. Vitamin D results were extracted from the laboratory information system without patient identification during 2011 and 2012 and separated by season and vitamin D results: less than 10ng/mL (deficient), 10-20.0ng/mL (insufficient), 20.1-30ng/mL (borderline), 30.1-40ng/mL (sufficient), 40.1-100ng/mL, and greater than 100ng/mL. RESULTS: The seasonal winter period constituted the months of January through March; spring, April through June; summer, July through September; and fall, October through December. The data set analyzed included 36,643 samples during the winter, 38,299 in spring, 36,141 in summer, and 37,738 in fall and demonstrated an expected rise and fall in vitamin D levels. CONCLUSION: This retrospective epidemiological study demonstrates seasonal variation of vitamin D levels at clinical decision points. Although not unexpected, this variation has an impact on studies relating low vitamin D levels to higher rates of cancer, cardiovascular disease, multiple sclerosis, diabetes, autoimmune disease, and a host of other health risk assessments.

The effect of complimentary and alternative medicine products on laboratory testing.

A multi-billion dollar industry has evolved over the last decade based on herbal product sales with an underlying belief that herbals are natural and therefore safe. The herbal product industry is essentially unregulated and producers are not required to follow good manufacturing practices (GMP). Batch to batch product variation, heavy metal and pesticide contamination, and even therapeutic drug contamination are problematic. Compounding these manufacturing issues are drug to drug and drug to herbal interactions that can cause cytochrome induction or inhibition. It is important for physicians to query their patients on herbal use and educate them on the potential adverse reactions. Herbals have been used for thousands of years and undoubtedly have demonstrated health benefits. However, more research is needed to gain an understanding of the complexity issues from mechanism of action to interference with clinical laboratory testing.