Recent Vitamin D Data from NHANES: Variability, Trends, Deficiency and Sufficiency Rates, and Assay Compatibility Issues

Objective: The primary purpose of this study was to evaluate compatibility between 2001-2006 and 2007-2010 data from National Health and Nutrition Examination Survey. Methods: NHANES used a radioimmunoassay to measure 25OHD levels in serum for 2001-2006 25OHD levels but a LC-MS/MS assay to measure 25OHD levels for 2007-2010.  However, regression equations built to derive LC-MS/MS compatible data from radioimmunoassay data for 2001-2006 were used to and make available LC-MS/MS compatible data for 2001-2006 also. Actual data released in public domain were statistically analyzed to measure supposed compatibility between 2001-2006 and 2007-2010 data. Results: The compatibility between derived data for 2001-2006 and direct measurement data for 2007-2010 could not be confirmed for studying trends in 25OHD levels, vitamin D deficiency rates, and vitamin D sufficiency rates because of unusually large shifts in these statistics between 2001-2006 and 2007-2010. Based on 2007-2010 data, the order of mean 25OHD levels and vitamin D sufficiency rates by race/ethnicity was: non-Hispanic white (NHW) > Mexican American (MA) > non-Hispanic black (NHB) and sufficiency rate was as low as 2.8% for NHB 12-19 years old. The order of vitamin D deficiency rates by race/ethnicity was: NHB > MA > NHW and deficiency rate was as high as 17% for 20-64 years old NHB. Females had higher mean 25OHD levels than males except for age groups 6-11 and 12-19 years old. Females had higher vitamin deficiency rates than males and the deficiency rate for females was as high as 4.5% for those aged 12-19 and 65+ years old. Females had higher sufficiency rates than males except for 6-11 years old and the sufficiency rate for females was as high as 47.2% for 65+ years old. Conclusion: Recent release of 25OHD data from NHANES for 2001-2006 was not found to be compatible with 2007-2010 NHANES data.