Fig 1.
Flow diagram of the study selection process.
Table 1.
Characteristics of the included studies.
rD: correlation between Vitamin D and DAS28; rE: correlation between Vitamin D and ESR; rC: correlation between Vitamin D and CRP; A: DAS28≥2.6; B: DAS28<2.6; NG: not given; RIA: radio-immunoassay; CLIA: chemiluminescent immunoassay; HPLC: high-performance liquid chromatography; ELISA: enzyme-linked immunosorbent assay; LCMS/MS: liquid chromatography tandem mass spectrometry; US: United States; ACR: American College of Rheumatology; EULAR: European League Against Rheumatism.
Fig 2.
Forest plot of serum vitamin D values in RA patients and healthy controls using continuous variance methods.
Fig 3.
Forest plot of serum vitamin D values in RA patients and healthy controls using dichotomous variance methods.
Fig 4.
Forest plots of disease activity and serum vitamin D levels in RA patients.
Summary of Fisher’s z tests with corresponding 95% confidence intervals for the relationship between: A) serum vitamin D levels and DAS28 scores; B) serum vitamin D levels and serum CRP levels; C) serum vitamin D levels and erythrocyte sedimentation rate.
Table 2.
The main statistical results concerning vitamin D and RA disease activity.
F: fixed-effects model; N: the relationship between vitamin D and RA was not statistically significant, and therefore we did not assess Venice Criteria grade.
Fig 5.
Forest plots of subgroup analysis focused on the relationship between serum vitamin D levels and disease activity scores in RA patients.
Summary of Fisher’s z scores with corresponding 95% confidence intervals for the relationship between serum vitam D levels and DAS28 scores: A) stratified according to latitude; B) stratified according to economic status.
Table 3.
F: fixed effects model; R: random effects model.