Baseline Characteristics Associated with Vitamin D Deficiency in Sickle Cell Disease and the Effect of Vitamin D Replacement

African Americans have lower vitamin D levels than the general population, which is thought to be due to decreased utilization of ultraviolet rays to convert vitamin D into an active form. Sickle cell patients have even lower vitamin D levels than African American controls. Preliminary studies at Tulane University correlated low vitamin D levels with markers of hemolysis (decreased hemoglobin (Hgb), increased reticulocyte count and lactate dehydrogenase (LDH)). Our main question was whether vitamin D deficiency in sickle cell patients is due to lack of outdoor activity or diet, or increased vitamin D metabolism during bone marrow turnover secondary to hemolysis.

80 adult sickle cell patients received pain, dietary, and outdoor activity level surveys. Vitamin D 25-hydroxy (25(OH)D), hemolytic lab markers (Hgb, Hct, LDH, total bilirubin, and reticulocyte count) were obtained.

Baseline Assessment: Vitamin D levels were available on 70 patients: 24.3% were normal or mildly deficient (≥20 ng/mL), 30% moderately deficient (10-<20 ng/mL), and 45.7% severely deficient (<10 ng/mL). We could not verify a correlation between LDH and 25(OH)D levels, but there was a trend towards increased total bilirubin in patients severely deficient in vitamin D (p = 0.06). Severely anemic patients (Hgb 5-<7 gm/dL) had significantly lower average 25(OH)D levels (p = 0.02). When comparing patients with moderately and severely deficient 25(OH)D levels to patients with no or mild deficiency, there was a significantly increased use of healthcare facilities (see Table 1 ). Though there was no significant difference in intake of fish, cheese, or eggs, there was a significant decrease in milk intake (see Table 1). There was no significant difference in days spent in bed or time spent outdoors (see Table 1).

Subjectively, patients did not report increased frequency of mild to moderate pain, vasocclusive crises, or use of pain medications in the moderately and severely vitamin D deficient groups but they did report higher rates of hospitalization due to sickle cell crises (p = 0.03, 0.005 respectively).

Effects of Vitamin D replacement: 56 patients took vitamin D replacement. After replacement, there was no difference in frequency of pain and pain medicine use, or days in the hospital and ER. However, pain levels appeared to be less intense (see Table 2). There was a trend towards fewer days spent in the hospital and ER (p = 0.089) in the 6 months following vitamin D replacement and there were significantly fewer Sickle Cell Day Hospital visits (p = 0.037).

Though we could not correlate vitamin D deficiency with LDH as a marker of hemolysis, lower Hgb levels seemed to be predictive of more severe vitamin D deficiency. Patients with more severe vitamin D deficiency did not report to have increased pain frequency or pain medication use, but had more ER visits and hospitalizations. When vitamin D was replaced, it did not decrease pain frequency, but it did decrease severity. We conclude that vitamin D replacement could lessen pain in sickle cell patients and thus utilization.

Kruse-Jarres:Bayer: Consultancy; Grifols: Consultancy; Talecris: Consultancy; Inspiration: Consultancy; NovoNordisk: Consultancy; Baxter: Consultancy.