Vitamin D Deficiency Treatment Patterns in Academic Urban Medical Center
Published Online: February 19, 2014
Paulette D. Chandler, MD, MPH; Edward L. Giovannucci, MD, ScD; Michelle A. Williams, ScD; Meryl S. LeBoff, MD; David W. Bates, MD, MSc; and LeRoi S. Hicks, MD, MPH
Vitamin D deficiency, defined as a 25-hydroxyvitamin D (25OHD) level less than 20 ng/mL, is widespread due to low dietary intake, low supplement use, and sun avoidance.1,2 Vitamin D deficiency is associated with a myriad of costly diseases including fractures,3-7 sepsis,8-13 and cancer.14-17 Higher healthcare costs associated with vitamin D deficiency are linked with increased length of hospital stay, surgical intensive care unit cost, and mortality rate.18-20 Furthermore, the risk of all-cause mortality is inversely related to 25OHD level.21-23 Overall, 25OHD levels among blacks tend to be one-third to one-half those of whites.24-26 As a result, 25OHD levels represent an important health issue in this group.
Serum 25OHD is a reliable method for evaluating vitamin D stores in patients. Although the desirable 25OHD range for patients needs to be more accurately defi ned, the Institute of Medicine (IOM) recommends that 25OHD be above 20 ng/mL to ensure that 97.5% of the population is vitamin D replete for optimal bone health.27 Higher levels may be needed to provide extraskeletal benefits.28 Furthermore, vitamin D supplementation can prevent and treat vitamin D deficiency.
To date, there are limited data on sex, racial, and ethnic differences in vitamin D prescribing for vitamin D deficiency. The goal of this study was to evaluate treatment of vitamin D deficiency (25OHD <20 ng/mL) in a racially diverse ambulatory practice affiliated with an academic urban medical center to determine the presence of racial/ethnic or sex disparities in use of vitamin D supplementation. Exploration of the process of ordering the test or determining why patients get the test is beyond the scope of this study.
Study Setting and Participants
The Human Studies Institutional Review Board committee of Partners HealthCare System approved the study protocol. We used the Research Patient Data Registry, a research and administrative data source designed to identify patients who meet specified criteria, through a query tool. We identified 11,454 adult patients (aged 18-102 years) receiving care in 1 of 16 ambulatory practices affi liated with an academic medical center who had 25OHD levels checked between January 1, 2004, and December 31, 2008. We restricted the present study to a single clinic because it was the most demographically diverse clinic. With the largest patient population of the 16 ambulatory practices, it has 31 attending physicians, 2 nurse practitioners, and no physician assistants. Furthermore, it has the largest black population of the 16 practices (24.8% black, 47.7% white, 14.1% Hispanic). We eliminated 1790 patients belonging to racial/ethnic categories other than non-Hispanic black, Hispanic, and non-Hispanic white because of small numbers and/or because patients had missing race/ethnicity data (Figure).
From these cross-sectional data, we selected 11,454 self-identified non-Hispanic black, Hispanic, and non- Hispanic white patients who were seen in the same primary care clinic within the 12 months before their first 25OHD measurement during the study period to ensure that enrollees were regular ambulatory patients in this system. From this group, we identified 2140 patients with 25OHD less than 20 ng/mL and with no diagnosis of renal disease. Patients with renal disease were excluded based on Elixhauser criteria for renal failure. Thus, the final sample consisted of 2140 eligible patients with 25OHD deficiency for our electronic medical record (EMR) review.
Medical Record Review
For each participant, we abstracted EMR data including participants’ demographic and clinical characteristics. Data elements obtained from each record included patients’ self-identified race/ethnicity (non-Hispanic black, Hispanic, or non-Hispanic white), sex, insurance status, comorbid conditions, and age. For each patient we also obtained the 25OHD level, date of 25OHD measurement, type of vitamin D prescribed within 30 days of 25OHD measurement, and date of vitamin D prescription.
For this study, we selected treatment of vitamin D defi ciency with a prescription of 50,000 units of ergocalciferol (vitamin D2) once weekly (7140 IU/day) or other forms of vitamin D including calcium/ergocalciferol 200 to 400 IU, cholecalciferol 400 to 1000 IU, or ergocalciferol 400 to 800 IU. The Endocrine Society Task Force guidelines state that all vitamin D–deficient adults should be treated with 50,000 IU of vitamin D2 or D3 once a week for 8 weeks or its equivalent of 6000 IU of vitamin D2 or D3 daily to achieve a blood level of 25OHD above 30 ng/mL.29 Data regarding treatment were obtained from each patient’s electronic medical record. We analyzed whether 50,000 IU of ergocalciferol or other forms of vitamin D was prescribed within 30 days of a 25OHD laboratory result less than 20 ng/mL.
A comorbidity index was calculated using the Elixhauser code method. The Elixhauser code method assigns points to 29 different diseases. Version 3.6 of Elixhauser codes was used (http://www.hcup-us.ahrq.gov/toolssoftware/ comorbidity/comorbidity.jsp). Points for each code were assigned based on the work of van Walraven and colleagues.30 The score was calculated based on the International Classification of Diseases, Ninth Revision codes for patients’ diseases documented on the day of the vitamin D test or on the day nearest that of the vitamin D test. Elixhauser comorbidity codes are condensed to a single numeric score that summarizes disease burden and is adequately discriminative for death in hospital. A higher score represents greater disease burden.30
We evaluated how frequently different types of vitamin D supplements were prescribed within 30 days for patients with a laboratory diagnosis of serum 25OHD deficiency. We then developed a series of logistic regression models to examine the association of patients’ socioeconomic characteristics and comorbidities with the outcome of prescribing high-dose vitamin D or other forms of vitamin D within 30 days of a laboratory diagnosis of serum 25OHD deficiency. Insurance status was dichotomized as Medicare, Medicaid, and self-pay versus private insurance. Age was dichotomized as less than 65 years and 65 years or older. Comorbidity score was dichotomized as 0 and greater than 0 based on the median Elixhauser comorbidity score of 0 for the study population. We then conducted multivariable logistic regression modeling to examine the independent association of patients’ race/ethnicity with differences in prescribing of high-dose vitamin D or other forms of vitamin D, adjusting for patient age, sex, insurance status, and Elixhauser comorbidity score. For each patient’s characteristics, we report adjusted odds ratios (ORs) and 95% confidence intervals (CIs) representing the odds of being prescribed high-dose vitamin D or some other form of vitamin D. We used SAS version 9.2 (SAS Institute, Inc, Cary, North Carolina) for the analysis.
Baseline Patient Characteristics
Among the 2140 patients evaluated for vitamin D deficiency, non-Hispanic white patients were significantly older, more likely to be privately insured, and had more comorbid diseases (Table 1). Among blacks, whites, and Hispanics, more women than men had vitamin D deficiency (women: 83.7%, 70.1%, and 80.8%, respectively; men: 16.3%, 29.9%, and 19.2%, respectively; Table 1). Most patients were aged less than 65 years (blacks 76.8%, whites 67.9%, Hispanics 79.3%; Table 1).
Of patients with identified comorbidities and vitamin D deficiency (n = 1396), hypertension was the most common comorbidity, present in 51.7% of blacks; 37.2% of whites, and 48% of Hispanics (Table 2). (Note: comorbidities were not available for all patients.)
Frequency and Likelihood of Vitamin D Therapy
Among the 11,454 patients tested for vitamin D status, 2140 (18.7%) were 25OHD deficient (Figure). From this group, we identified 723 non-Hispanic black, Hispanic, or non-Hispanic white patients prescribed some type of vitamin D within 30 days, 561 of whom received at least 1 prescription dose of 50,000 IU of ergocalciferol (Figure). High-dose ergocalciferol represented 77.6% of vitamin D medications prescribed during the 30-day period. Overall, only 33.8% of vitamin D–deficient patients received a vitamin D prescription within 30 days of diagnosis of vitamin D deficiency. Blacks and Hispanics received vitamin D prescriptions more often than whites: 37.8%, 38.4%, and 30.9%, respectively (P = .003; Table 3). The vitamin D prescription rate for women versus men was 26.3% and 7.5%, respectively (P = .003; Table 3). In unadjusted analyses, 25OHD-deficient women had 25% higher odds of getting a vitamin D prescription compared with men (P = .03; Table 4).
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