A descriptive study of vitamin D testing in a primary care cohort

From the 2021 HVPAA National Conference

Megan Sheehan (Cleveland Clinic Lerner College of Medicine), Michael Rothberg (Cleveland Clinic)

Background

Vitamin D is a common laboratory test ordered by primary care and specialist providers. Although vitamin D deficiency is thought to be common, the utility of population-level screening is unclear. The United States Preventative Services Task Force states there is insufficient evidence to recommend screening, and American Family Physician Guidelines do not recommend routine testing. Despite this, from 2000 to 2010, there was an 83-fold increase in testing for Medicare recipients. In 2013, the Choosing Wisely campaign recommended against screening in asymptomatic, otherwise healthy patients. It is unknown if these recommendations have changed practice.

Objective

To describe order indications, test results, and trends in vitamin D testing over a 12-year period in a primary care cohort.

Methods

The primary care cohort included patients seen at least twice from 2005-2019 at Cleveland Clinic internal medicine or family medicine clinics, and all tests ordered from 2008-2020 for these patients were included. Indications, entered by the ordering provider, and test results were analyzed for all 25-hydroxy vitamin D tests. Testing levels were categorized based on the National Academy of Medicine Dietary Reference Intakes and literature review as severely deficient (≤ 10 ng/mL), deficient (10-20 ng/mL), insufficient (20-30 ng/mL), sufficient (30-100 ng/mL) and toxic (≥ 100 ng/mL). Trends of testing over time were standardized by the unique number of ordering providers per year.

Results

Of 859,145 patients, 417,615 (48.6%) had vitamin D tests over this time period; 63% were ordered by primary care providers. The most common indications for testing were vitamin deficiency (32.4%), bone disorders (7.3%), routine medical examination (6.8%), fatigue or myalgia (6.8%), and chronic diseases including hypertension, hyperlipidemia, and diabetes (6.4%). Overall, 2.7% of test results showed severe deficiency, while 54.9% had sufficient levels of vitamin D. Only 0.3% of tests showed toxic levels of vitamin D.

There were 400,064 patients whose first vitamin D test was ordered from 2008-2020. Of those tests, 13.3% were ordered for vitamin deficiency, 12% for fatigue or myalgia, 11.2% for a routine medical examination, 7% for chronic diseases, and 5.1% for bone disorders. Only 37.2% of patients had sufficient vitamin D levels at this first test.

After peaking in 2009, the number of tests ordered per unique provider declined over the next decade. There was a sharp decline in the number of first tests ordered, while the number of repeat tests increased slightly over time (Figure).

Conclusions

Vitamin D tests are frequently ordered in a primary care patient cohort, often for non-specific indications such as fatigue or as part of a routine examination. Testing has declined over time, particularly initiation of testing for individual patients.

Clinical Implications

Vitamin D guidelines appear to have impacted physician decision making. The high rate of repeat testing suggests patient preferences may play a role, and patient education may help decrease inappropriate testing.

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