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 multi-variable 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 (similar to 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.