Increased rates of 25-hydroxy vitamin D testing: Dissecting a modern epidemic.

INTRODUCTION: Laboratories have noted marked increases in the analysis of 25-hydroxy vitamin D (25(OH)D) in recent decades. Our objectives were to describe the annual number of 25(OH)D tests, examine the characteristics of those tested and those ordering them, and determine the proportion of potentially unnecessary tests in Manitoba.

METHODS: Manitoba residents who were tested between 2006/7 and 2012/13 had their data anonymously linked to Manitoba Centre for Health Policy comprehensive administrative datasets. Patient and physician characteristics, location of residence, and 25(OH)D concentrations were determined. Descriptive statistics and multivariable regression models were utilized.

RESULTS: There was a quadrupling in testing from 2006 to 2013, with >20,000 tests performed in 2012/13. The median annual number of tests was one per patient; the maximum was >10 tests per year. Adult females had twice the number of tests compared to males (p < 0.001). There was a rise in 25(OH)D concentrations over time with hypervitaminosis D increasing disproportionately (2006/7 to 212/13 (0% vs. 0.15%, p < 0.001)). Apparently unnecessary testing rose by 1/3 over time, frequently ordered by Family Medicine practitioners. A revised 25(OH)D requisition resulted in striking reduction of 25(OH)D requests (~80%).

DISCUSSION: Manitoba noted a rapid increase in testing, and rise in 25(OH)D concentrations with levels that may be associated with toxicities; both have been reported in other jurisdictions. There appeared to a striking rise in 'unnecessary' tests. We similarly report the benefit of the implementation of a mandatory requisition specifying eligibility criteria for 25(OH)D and education about appropriate testing.