title: Current daily glucocorticoid use and serum creatinine levels are associated with lower 25(OH) vitamin D levels in Thai patients with systemic lupus erythematosus.
abstract: OBJECTIVE
  Because vitamin D deficiency has been previously reported in patients with systemic lupus erythematosus (SLE), we decided to examine the prevalence of vitamin D deficiency in Thai SLE patients, to identify possible independent factors affecting serum 25-hydroxyvitamin D(2) and D(3) [25(OH)] vitamin D levels, and to examine the associations of serum 25(OH) vitamin D and disease activity and damage in Thai SLE patients.
  
  
  METHODS
  A cross-sectional study was performed in 101 SLE patients. Blood samples were prospectively collected. The levels of 25(OH) vitamin D were measured by radioimmunoassay. The cutoffs for vitamin D deficiency and insufficiency were 30 and 20 ng/mL, respectively. Demographic, clinical, and laboratory data were collected, and their associations with 25(OH) vitamin D level were examined by univariate and multivariate linear regression analyses.
  
  
  RESULTS
  The level of 25(OH) vitamin D (mean [SD]) was 27.9 (7.6). Seventeen patients (17%) had vitamin D deficiency, 41 patients (41%) had vitamin D insufficiency, and 43 patients (42%) had normal vitamin D levels. Two thirds of the patients were taking relatively low-dose vitamin D supplementations. Current daily glucocorticoid dose and serum creatinine levels were negatively correlated with vitamin D levels (β = -0.207, P = 0.023; and β = -3.770, P = 0.003, respectively). There were no associations between disease activity or damage and 25(OH) vitamin D levels.
  
  
  CONCLUSIONS
  Vitamin D deficiency and insufficiency are common in SLE patients despite more than half of them taking vitamin D supplementations. Higher serum creatinine level and higher current daily glucocorticoid dose are associated with lower serum 25(OH) vitamin D levels. These patients may require higher doses of vitamin D supplementations.
authors.affiliation: Rheumatic Disease Unit, Department of Internal Medicine, Phramongkutklao Hospital and College of Medicine, Bangkok, Thailand. sumapac@yahoo.com
authors.forename: Sumapa
authors.initials: S
authors.lastname: Chaiamnuay
authors.forename: La-or
authors.initials: LO
authors.lastname: Chailurkit
authors.forename: Pongthorn
authors.initials: P
authors.lastname: Narongroeknawin
authors.forename: Paijit
authors.initials: P
authors.lastname: Asavatanabodee
authors.forename: Sukij
authors.initials: S
authors.lastname: Laohajaroensombat
authors.forename: Pornthita
authors.initials: P
authors.lastname: Chaiamnuay
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000328:Adult; D002112:Calcifediol / Q000097:blood*; D015897:Comorbidity; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000097:blood* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D012044:Regression Analysis; D013785:Thailand / Q000453:epidemiology; D014807:Vitamin D / Q000008:administration & dosage / Q000627:therapeutic use; D014808:Vitamin D Deficiency / Q000188:drug therapy / Q000453:epidemiology*
chemical_list: D005938:Glucocorticoids; D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2; D003404:Creatinine; D002112:Calcifediol