Background/Purpose:

Vitamin D deficiency is under-recognized and in 18-35% of patients who do not respond to bisphosphonates, concurrent use of vitamin D 1000 units daily increases bone mineral density (BMD) at the lumbar spine and femoral neck, and reduces hip and non-vertebral fractures^.Recent work has shown that patients with a serum vitamin D level at 30ng/ml or above are more likely to achieve improved BMD when treated with bisphosphonates. We undertook this study to identify how many of our patients have an adequate vitamin D level prior to starting and during bisphosphonate therapy.

We identified consecutive patients at our University based rheumatology clinic as well as our Veterans Affairs (VA) rheumatology clinic who were at the time on bisphosphonate therapy and conducted a retrospective chart review.  Information on age, gender, reason for bisphosphonate use, type of bisphosphonate, vitamin D levels, date levels were checked, and date of bisphosphonate prescription were obtained. Vitamin D deficiency was defined at levels <30ng/ml. A two-tailed Fisher Exact Test was used for statistical analysis of categorical variables and students t-test for continuous variables.

Results:

Sixty-eight patients on bisphosphonate therapy were identified from the two clinic sites out of which 24 were from the University clinic and 44 from the VA clinic. The VA patients were more likely to be men [91% vs. 21% (p=0.0001)] and older [68.5 + 10.8 vs. 58.8 + 11.4 (p=0.0008)]. Reasons for bisphosphonate therapy included chronic steroid use (N=30), osteoporosis (N=21), osteopenia and chronic steroids (N=5), osteoporosis and chronic steroids (N=4), Paget’s disease (N=3) and hypogonadism (N=1). Patients were either on zolendronate (N=13), alendronate (N=53) or risedronate (N=2). Vitamin D deficiency was identified in 47% of patients (mean vitamin D level = 22.2 ng/ml + 12.4). Vitamin D level was not checked in 29% of patients prior to initiation of bisphosphonate therapy, and when subsequently tested 21% of them were deficient. While there was no statistical significance of vitamin D deficiency between the two clinics, vitamin D level was checked more frequently prior to bisphosphonate therapy at the VA as compared to the University clinic [83.3% vs 43.5% (p =0.002)].

Conclusion:

We have shown that during bisphosphonate therapy 47% of our patients can be vitamin D deficient. Vitamin D was not checked prior to initiation of bisphosphonate therapy in 29% of our patients, this being more commonly the case at our University based clinic as compared to the VA based clinic, and from these patients who were subsequently tested 21% of them were deficient.  This may help explain a lack of response to bisphosphonates in many of our patients, and deserves consideration.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/determination-of-vitamin-d-level-prior-to-the-initiation-of-bisphosphonate-therapy/