Testing for vitamin D deficiency in veterans-is there a seasonal bias?

The present study was undertaken to determine if a seasonal bias was present for vitamin D testing among Northeast Tennessee veterans, in whom vitamin D deficiency is common.

Medical chart review.

VA Medical Center.

Participants were 9447 patients with initial 25(OH) vitamin D levels obtained over a 3-year period.

Serum 25-hydroxyvitamin D (25[OH]D) level, date of testing, patient background factors.

Vitamin D testing occurred more frequently in September, October, November, and December, whereas the lowest levels of 25(OH) vitamin D levels were found in January, February, and March. Similar results were observed in quarterly data with the greatest number of tests noted in the last quarter of the year, yet the lowest 25(OH) vitamin D levels were noted in the first quarter. The average monthly 25(OH) vitamin D levels were below 30 ng/mL throughout the year in the study population, consistent with highly prevalent vitamin D deficiency.

Clinicians may have a seasonal bias, favoring testing for vitamin D status in the latter part of the year even though the lowest vitamin D levels are observed in the first part of the year. Although an argument could be made to check for peak 25(OH) vitamin D levels in September and trough levels in March, the seasonal contribution to vitamin D deficiency is overshadowed by ongoing vitamin D deficiency throughout the year. Thus, it may be prudent to test for vitamin D deficiency in patients presenting with fatigue, myalgias, and arthralgias regardless of the season of presentation.