Table 4 Meta-analysis of studies reporting familial cases in different subgroups
Potential |  | Odd Ratio (CI 95%) | No of Studies | Heterogeneity χ2 | P value | I2 | Interaction p value |
|---|---|---|---|---|---|---|---|
A Homozygote model: MM vs. TT | |||||||
 Ethnicity | Caucasian | 1.204 (0.835–1.735) | 5 | 2.56 | 0.634 | 0.0% | 0.000 |
Mixed | 0.451 (0.309–0.659) | 3 | 1.8 | 0.406 | 0.0% | ||
 Study-based | Hospital-based | 1.184 (0.784–1.788) | 4 | 1.52 | 0.677 | 0.0% | 0.690 |
Population-based | 0.581 (0.318–1.060) | 4 | 8.24 | 0.041 | 63.6% | ||
 Methodological quality | Good | 1.080 (0.691–1.688) | 3 | 0.67 | 0.716 | 0.0% | 0.002 |
Fair | 0.504 (0.304–0.834) | 4 | 4.51 | 0.211 | 33.5% | ||
Poor | 1.449 (0.752–2.793) | 1 | 0.00 | . | .% | ||
 Case enrollment strategies | Incident | 1.000 (0.300–3.327) | 2 | 1.64 | 0.201 | 38.9% | 0.068 |
Prevalent | 0.683 (0.412–1.134) | 5 | 10.69 | 0.030 | 62.6% | ||
Not mentioned | 1.449 (0.752–2.793) | 1 | 0 | . | .% | ||
 All studies |  | 0.809 (0.521–1.258) | 8 | 17.7 | 0.013 | 60.4% | – |
B Dominant model: TM + MM vs. TT | |||||||
 Ethnicity | Caucasian | 1.012 (0.800–1.280) | 5 | 0.82 | 0.936 | 0.0% | 0.576 |
Mixed | 1.104 (0.909–1.341) | 3 | 0.39 | 0.824 | 0.0% | ||
 Study-based | Hospital-based | 1.016 (0.770–1.341) | 4 | 1.11 | 0.775 | 0.0% | 0.690 |
Population-based | 1.087 (0.910–1.299) | 4 | 0.25 | 0.969 | 0.0% | ||
 Methodological quality | Good | 1.132 (0.855–1.499) | 3 | 0.13 | 0.937 | 0.0% | 0.614 |
Fair | 1.075 (0.887–1.304) | 4 | 0.41 | . 0.937 | 0.0% | ||
Poor | 0.868 (0.553–1.364) | 1 | 0.00 | . | .% | ||
 Case enrollment strategies | Incident | 0.958 (0.530–1.733) | 2 | 0.39 | 0.201 | 38.9% | 0.579 |
Prevalent | 1.104 (0.936–1.302) | 5 | 0.03 | 0.856 | 0.0% | ||
Not mentioned | 0.868 (0.553–1.364) | 1 | 0 | . | .% | ||
 All studies |  | 1.066 (0.917–1.238) | 8 | 1.52 | 0.982 | 0.0% | – |
C Recessive model: MM vs. TM + TT | |||||||
 Ethnicity | Caucasian | 1.233 (0.877–1.732) | 5 | 3.41 | 0.491 | 0.0% | 0.576 |
Mixed | 0.462 (0.298–0.716) | 3 | 2.65 | 0.266 | 24.5% | ||
 Study-based | Hospital-based | 1.224 (0.834–1.796) | 4 | 1.25 | 0.742 | 0.0% | 0.690 |
Population-based | 0.409 (0.228–0.734) | 4 | 10.89 | 0.012 | 72.4% | ||
 Methodological quality | Good | 1.172 (0.765–1.793) | 3 | 0.79 | 0.675 | 0.0% | 0.614 |
Fair | 0.515 (0.297–0.894) | 4 | 5.63 | 0.131 | 46.7% | ||
Poor | 1.389 (0.770–2.508) | 1 | 0.00 | . 2.508 | – | ||
 Case enrollment strategies | Incident | 0.977 (0.258–3.707) | 5 | 14.05 | 0.007 | 71.5% | 0.579 |
Prevalent | 0.718 (0.410–1.257) | 2 | 2.36 | 0.124 | 57.7% | ||
Not mentioned | 1.389 (0.770–2.508) | 1 | 0.00 | – | – | ||
 All studies |  | 0.831 (0.524–1.319) | 8 | 21.53 | 0.003 | 67.5% | – |