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Table 2 Results of subgroup analysis

From: Vitamin D deficiency associated with Crohn’s disease and ulcerative colitis: a meta-analysis of 55 observational studies

Subgroup analyses Crohn disease Ulcerative colitis
No. of effect sizes Mean (95% CI) P for mean I2 (%) No. of effect sizes Mean (95% CI) P for mean I2 (%)
25(OH)D among disease patients and healthy controls
 Maturity
  Adults (> 18 years old) 24 − 3.22 (− 4.75 to − 1.70) < 0.01 90 11 − 2.38 (− 4.20 to − 0.56) < 0.01 85
  Children (< 18 years old) 8 − 3.61 (− 4.89 to − 2.32) < 0.01 90 4 − 4.45 (− 9.42 to 0.53) < 0.01 78
 Vitamin D assessment tool
  CLIA 5 − 1.32(− 8.89 to 6.26) < 0.01 95 2 − 3.10 (− 7.50 to 1.30) 0.2 38
  CLIA + LC–MS 1 − 0.20 (− 2.90 to 2.50) NR NR 0 NR NR NR
  CPBA 5 − 4.28 (− 6.40 to − 2.16) 0.06 55 1 − 1.10 (− 2.31 to 0.11) NR NR
  ELISA 6 − 8.29 (− 13.83 to − 2.76) < 0.01 85 3 − 8.22 (− 16.62 to 0.19) < 0.01 86
  HPLC 3 − 3.23 (− 9.40 to 2.95) 0.09 58 1 − 7.00 (− 11.58 to − 2.42) NR NR
  LC–MS 3 − 0.35 (− 0.99 to 0.29) 0.25 27 2 − 0.15 (− 0.57 to 0.27) 0.77 0
  RIA 8 − 4.46 (− 9.05 to 0.13) < 0.01 90 4 − 4.52 (− 12.89 to 3.85) < 0.01 89
  NR 1 3.11 (− 3.37 to 9.59) NR NR     
 Vitamin D supplementation
  No 24 − 3.46 (− 4.90 to − 2.03) < 0.01 91 12 − 3.29 (− 4.99 to − 1.60) < 0.01 87
  Yes 7 − 1.49 (− 4.40 to 1.42) < 0.01 66 3 0.72 (− 1.98 to 3.41) 0.95 0
  NR 1 − 12.14 (− 19.54 to − 4.74) NR NR 0 NR NR NR
 Study design
  Case–control study 19 − 4.95 (− 7.85 to − 3.11) < 0.01 89 7 − 2.24 (− 4.59 to 0.11) < 0.01 79
  Cohort study 9 − 2.11 (− 3.69 to -0.53) < 0.01 82 4 − 2.58 (− 5.29 to 0.13) < 0.01 89
  Cross-sectional study 4 − 0.44 (− 6.76 to 5.87) < 0.01 93 1 − 18.07 (− 26.50 to -9.64) NR NR
25(OH)D among disease patients and non-healthy controls
 Maturity
  Adults (> 18 years old) 28 − 0.84 (− 2.12 to 0.44) < 0.01 85 26 0.65 (− 0.65 to 1.95) < 0.01 86
  Children (< 18 years old) 9 0.53 (− 2.16 to 3.22) < 0.01 78 8 0.92 (− 2.05 to 3.90) < 0.01 79
  NR 1 − 1.88 (− 5.52 to 1.76) NR NR 1 1.88 (− 1.76 to 5.52) NR NR
 Vitamin D assessment tool
  CLIA 7 1.66 (− 1.36 to 4.68) < 0.01 73 6 − 0.81 (− 3.96 to 2.43) < 0.01 73
  CPBA 7 − 0.80 (− 2.79 to 1.20) < 0.01 76 6 1.94(− 0.03 to 3.91) < 0.01 78
  ECLIA 2 1.34 (0.17 to 2.52) 0.62 0 2 − 1.34 (− 2.52 to − 0.17) 0.23 31
  ELISA 4 1.60 (− 5.26 to 2.07) < 0.01 84 1 0.18 (− 3.65 to 4.01) NR NR
  HPLC 2 − 3.27 (− 6.35 to 0.19) 0.53 0 1 3.69 (0.34 to 7.04) NR NR
  LC–MS 2 0.96 (− 0.84 to 2.76) 0.02 80 2 − 0.96 (− 2.76 to 0.84) 0.02 80
  RIA 10 − 1.65 (− 5.16 to 1.86) < 0.01 85 9 1.18 (− 2.61 to 4.98) < 0.01 87
  NR 4 − 2.35 (− 4.91 to − 0.20) 0.67 0 2 2.35 (− 0.20 to 4.91) 0.45 0
 Vitamin D supplementation
  No 34 − 0.48 (− 1.70 to 0.74) < 0.01 84 31 − 0.71 (− 0.63 to -2.05) < 0.01 85
  Yes 4 − 2.36 (− 3.25 to − 1.46) 0.45 0 3 2.36 (1.46 to 3.25) 0.45 19
 Study design
  Case–control study 12 − 0.07 (− 1.77 to 1.64) < 0.01 58 9 0.91 (− 1.09 to 2.91) 0.37 68
  Cohort study 10 0.46 (− 1.28 to 2.20) < 0.01 74 16 0.09 (− 1.52 to 1.69) 0.92 78
  Cross-sectional study 10 − 0.56 (− 4.21 to 3.10) < 0.01 91 9 1.47 (− 1.56 to 4.50) 0.34 91
1,25(OH)2D3 among disease patients and healthy controls
 Maturity
  Adults (> 18 years old) 5 0.31 (− 12.88 to 13.50) < 0.01 96 3 − 2.94 (− 7.25 to 1.38) 0.11 55
  Children (< 18 years old) 3 8.64 (− 14.08 to 31.35) < 0.01 99 2 16.54 (− 2.85 to 35.94) 0.01 84
 Vitamin D assessment tool
  CPBA 1 15.70 (15.20 to 16.20) NR NR 1 − 0.80 (− 1.86 to 0.26) NR NR
  HPLC 1 − 8.62 (− 21.62 to 4.38) NR NR NR NR NR NR
  RIA 5 3.07 (− 13.33 to 19.47) < 0.01 97 3 4.31 (− 20.38 to 28.99) < 0.01 97
  NR 1 3.20 (− 1.16 to 7.56) NR NR 1 5.30 (− 9.49 to 20.09) NR NR
 Vitamin D supplementation
  No 8 3.47 (− 7.72 to 14.66) < 0.01 98 5 3.76 (− 8.36 to 15.87) < 0.01 96
 Study design
  Case–control study 6 3.95 (− 9.09 to 16.98) < 0.01 95 4 4.60 (− 15.56 to 24.77) < 0.01 96
  Cohort study 2 2.14 (− 24.51 to 28.80) < 0.01 100 1 − 0.80 (− 1.86 to 0.26) NR NR
1,25(OH)2D3 among disease patients and non-healthy controls
 Maturity
  Adults (> 18 years old) 6 6.77 (− 2.30 to 15.84) < 0.01 98 4 − 10.48 (− 21.86 to 0.89) < 0.01 96
  Children (< 18 years old) 3 1.40 (− 9.11 to 11.90) 0.06 64 3 − 1.40 (− 11.90 to 9.11) 0.06 64
 Vitamin D assessment tool
  CPBA 2 6.07 (− 15.64 to 27.79) < 0.01 94 2 − 6.07 (− 27.79 to 15.64) < 0.01 94
  HPLC + RIA 1 − 0.08 (− 4.59 to 4.43) NR NR 0 NR NR NR
  RIA 4 0.87 (− 1.14 to 2.87) 0.11 55 3 − 3.51 (− 10.10 to 3.09) 0.11 55
  NR 2 10.93 (− 13.44 to 35.31) < 0.01 86 2 − 10.93 (− 35.31 to 13.44) < 0.01 86
 Vitamin D supplementation
  No 9 5.05 (− 2.42 to 12.52) < 0.01 97 7 − 6.71 (− 15.30 to 1.88) < 0.01 94
 Study design
  Case–control study 6 0.60 (− 1.36 to 2.56) 0.26 23 5 − 1.00 (− 4.08 to 2.08) 0.17 37
  Cohort study 2 16.57 (15.47 to 17.66) 0.25 24 2 − 16.57 (− 17.66 to − 15.47) 0.25 24
  Cross-sectional study 1 − 0.08 (− 4.59 to 4.43) NR NR 0 NR NR NR
  1. CPBA competitive protein binding assay, RIA radioimmunoassay, ECLIA electrochemiluminescence immunoassay, ELISA enzyme-linked immunosorbent assay, CLIA chemiluminescence, HPLC high performance liquid chromatograph, LC–MS liquid chromatograph mass spectrometer, NR not reported