Purpose: To assess the prevalence of vitamin D deficiency in patients on hemodialysis upon admission to a long term acute care hospital, as well as to examine characteristics of these individuals, with the purpose of identifying possible risk factors for vitamin D deficiency in kidney failure.
Subjects: 56 hemodialysis patients who were admitted on or began treatment with hemodialysis and were under the care of Dr. Patrick McCullough at the Drake Rehabilitation Center in Cincinnati, OH between June 2009 and December 2010 were included in this study.
Study Design and Methods: Data for this study were obtained as part of a retrospective observational cohort study of patients on hemodialysis who received vitamin D supplementation as standard of care while admitted to a LTACH. Patient data for this study were collected pre-supplementation at the baseline assessment visit. Biochemical data included 25(OH) D levels, 1, 25(OH)2 D levels, Parathyroid hormone (PTH), serum calcium, and serum albumin. Demographic information and medical history were collected retrospectively from chart review. For analysis, patients were categorized into three groups based on widely used cutoffs for serum 25(OH) D in Chronic Kidney Disease; vitamin D sufficient (>30 ng/mL), vitamin D insufficient (<30 ng/mL but >10 ng/mL) and vitamin D deficient (<10 ng/mL). Differences were then explored between the groups for biochemical data, demographic information, and medical history.
Results: Seven percent (n=4) of the patients in the cohort were vitamin D sufficient, 48% (n=27) were vitamin D insufficient and 45% (n=25) were vitamin D deficient upon admission. No patients were diagnosed with a vitamin D deficiency prior to admission. As expected, vitamin D supplementation upon admission was related to vitamin D group assignment with a greater number of sufficient patients being supplemented with vitamin D than in the other groups. The vitamin D deficient group was significantly younger than the vitamin D insufficient group. No differences were observed between vitamin D groups for mean serum calcium, albumin or PTH levels or number of individuals who had suboptimal levels of these analytes. The majority of patients in the cohort had suboptimal levels of both serum calcium and albumin. Notably, PTH levels met established targets in only 4 participants with suboptimal vitamin D status.
Conclusion: Based on these findings, the prevalence of vitamin D insufficiency and deficiency among patients with renal disease admitted to a LTACH is high, and vitamin D inadequacy is commonly undiagnosed in this at risk population. No specific demographic or clinical characteristics examined in this study were related to vitamin D deficiency grouping. The National Kidney Foundation's guideline to assess 25 (OH) vitamin D in patients on dialysis if PTH levels exceed 300 pg/mL is likely to miss a significant number of individuals with suboptimal vitamin D status.
Limitations: It is difficult to determine risk factors for a specific condition from a retrospective study. This study also had a small sample size and a limited number of patients in the vitamin D sufficient group, reducing the power of the study to detect group differences if they exist.