Table 3.
Summary ORs and heterogeneity results for associations between the MTHFR C677T polymorphism and DR.
| Subgroup | Genetic Model | Studies No (All/Sensitivity) | OR (95% CI) | p * | I2 (%) | OR se (95% CI) # |
|---|---|---|---|---|---|---|
| Overall | CT vs. CC | 18/15 | 1.46 (1.15–1.86) | 0.00 | 60.0 | 1.32 (1.02–1.70) |
| TT vs. CC | 18/15 | 2.45 (1.66–3.60) | 0.00 | 69.0 | 2.27 (1.44–3.58) | |
| Allele contrast | 18/15 | 1.52 (1.26–1.84) | 0.00 | 72.4 | 1.45 (1.17–1.79) | |
| Recessive model | 18/15 | 1.67 (1.19–2.40) | 0.00 | 71.9 | 1.87 (1.32–2.66) | |
| Dominant model | 18/15 | 1.71 (1.28–2.28) | 0.00 | 75.3 | 1.50 (1.13–1.98) | |
| Asian | CT vs. CC | 12/9 | 1.71 (1.22–2.39) | 0.00 | 64.9 | 1.52 (1.01–2.30) |
| TT vs. CC | 12/9 | 2.97 (2.06–4.29) | 0.02 | 51.5 | 3.07 (1.83–5.14) | |
| Allele contrast | 12/9 | 1.75 (1.42–2.18) | 0.00 | 67.3 | 1.69 (1.28–2.24) | |
| Recessive model | 12/9 | 2.16 (1.75–2.65) | 0.11 | 35.1 | 2.34(1.62–3.38) | |
| Dominant model | 12/9 | 1.98 (1.42–2.76) | 0.00 | 68.6 | 1.83 (1.20–2.81) | |
| Non-Asian | CT vs. CC | 6/6 | 1.15 (0.92–1.45) | 0.38 | 5.4 | 1.15 (0.92–1.45) |
| TT vs. CC | 6/6 | 1.33 (0.69–2.54) | 0.04 | 61.4 | 1.33 (0.69–2.54) | |
| Allele contrast | 6/6 | 1.14 (0.89–1.46) | 0.07 | 51.5 | 1.14 (0.89–1.46) | |
| Recessive model | 6/6 | 1.24 (0.69–2.23) | 0.05 | 57.7 | 1.24 (0.69–2.23) | |
| Dominant model | 6/6 | 1.18 (0.95–1.47) | 0.21 | 30.70 | 1.18 (0.95–1.47) | |
| T2DM | CT vs. CC | 12/10 | 1.50 (1.08–2.09) | 0.00 | 66.5 | 1.32 (0.93–1.86) |
| TT vs. CC | 12/10 | 2.68 (1.74–4.13) | 0.00 | 66.2 | 2.61 (1.50–4.53) | |
| Allele contrast | 12/10 | 1.59 (1.26–2.01) | 0.00 | 74.0 | 1.49 (1.14–1.96) | |
| Recessive model | 12/10 | 2.05 (1.47–2.84) | 0.01 | 56.9 | 2.10 (1.38–3.17) | |
| Dominant model | 12/10 | 1.72 (1.23–2.42) | 0.00 | 72.1 | 1.54 (1.06–2.24) | |
| Non-T2DM | CT vs. CC | 6/5 | 1.30 (1.02–1.66) | 0.12 | 43.5 | 1.32 (0.89–1.97) |
| TT vs. CC | 6/5 | 1.75 (0.93–3.27) | 0.05 | 55.9 | 1.70 (0.80–3.63) | |
| Allele contrast | 6/5 | 1.38 (1.02–1.88) | 0.02 | 64.5 | 1.34 (0.95–1.91) | |
| Recessive model | 6/5 | 1.38 (0.96–2.00) | 0.14 | 39.5 | 1.32 (0.89–1.97) | |
| Dominant model | 6/5 | 1.46 (1.00–2.13) | 0.04 | 57.4 | 1.42 (0.92–2.19) | |
| Asian with T2DM | CT vs. CC | 9/7 | 1.64 (1.07–2.50) | 0.00 | 73.8 | 1.40 (0.86–2.29) |
| TT vs. CC | 9/7 | 3.00 (1.92–4.68) | 0.01 | 63.8 | 2.99 (1.63–5.50) | |
| Allele contrast | 9/7 | 1.73 (1.33–2.26) | 0.00 | 76.0 | 1.64 (1.17–2.29) | |
| Recessive model | 9/7 | 2.21 (1.59–3.06) | 0.03 | 51.9 | 2.33 (1.52–3.57) | |
| Dominant model | 9/7 | 1.94 (1.27–2.94) | 0.00 | 76.7 | 1.72 (1.03–2.89) | |
| Asian with Non-T2DM | CT vs. CC | 3/2 | 1.99 (1.22–3.25) | 0.87 | 0.0 | 2.19 (1.19–4.01) |
| TT vs. CC | 3/2 | 2.80 (1.39–5.66) | 0.77 | 0.0 | 3.50 (1.28–9.62) | |
| Allele contrast | 3/2 | 1.86 (1.32–2.60) | 0.90 | 0.0 | 1.97 (1.28–3.05) | |
| Recessive model | 3/2 | 2.06 (1.06–4.02) | 0.87 | 0.0 | 2.38 (0.91–6.24) | |
| Dominant model | 3/2 | 2.17 (1.38–3.42) | 0.85 | 0.0 | 2.40 (1.35–4.28) | |
| Non-Asian with T2DM | CT vs. CC | 3/3 | 1.20 (0.81–1.76) | 0.79 | 0.0 | 1.20 (0.81–1.76) |
| TT vs. CC | 3/3 | 1.54 (0.43–5.46) | 0.08 | 68.2 | 1.54 (0.43–5.46) | |
| Allele contrast | 3/3 | 1.18 (0.90–1.56) | 0.25 | 27.0 | 1.18 (0.90–1.56) | |
| Recessive model | 3/3 | 1.37 (0.39–4.82) | 0.06 | 70.8 | 1.37 (0.39–4.82) | |
| Dominant model | 3/3 | 1.24 (0.86–1.80) | 0.58 | 0.0 | 1.24 (0.86–1.80) | |
| Non-Asian with Non-T2DM | CT vs. CC | 3/3 | 1.09 (0.69–1.71) | 0.09 | 58.0 | 1.09 (0.69–1.71) |
| TT vs. CC | 3/3 | 1.24 (0.49–3.14) | 0.03 | 71.9 | 1.24 (0.49–3.14) | |
| Allele contrast | 3/3 | 1.13 (0.76–1.68) | 0.02 | 73.3 | 1.13 (0.76–1.68) | |
| Recessive model | 3/3 | 1.21 (0.54–2.72) | 0.05 | 66.9 | 1.21 (0.54–2.72) | |
| Dominant model | 3/3 | 1.13 (0.69–1.83) | 0.05 | 66.7 | 1.13 (0.69–1.83) |
# OR se: Sensitivity analysis OR for HWE; * Test for heterogeneity: random-effects model was used when p value for heterogeneity test <0.05 and I2 > 50%; otherwise, fixed-effects model was used; T2DM, type 2 diabetes mellitus;Non-T2DM, type 1 diabetes mellitus or unknown DM type or mixed DM type; Non-Asian, Caucasian and African-American population.