Table 2 Evaluation of study quality
Study | Selection | Comparability | Exposure | Scores | |||||
|---|---|---|---|---|---|---|---|---|---|
Adequate definition of cases | Representativeness of the cases | Selection of controls | Definition of controls | Control for important factor | Ascertainment of exposure | Same method of ascertainment for cases andcontrols | Non-response rate | ||
Grimm MO al. 2002 [25] | ☆ | ☆ | ☆ | ☆ | / | ☆ | ☆ | ☆ | 7 |
Thomas Steuber al. 2011 [26] | ☆ | ☆ | ☆ | ☆ | / | ☆ | ☆ | ☆ | 7 |
Axel Heidenreich al. 2015 [27] | / | ☆ | ☆ | ☆ | ☆ | ☆ | / | ☆ | 6 |
Bimal Bhindi al. 2017 [28] | / | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | 7 |
M Moschini al. 2016 [29] | ☆ | ☆ | ☆ | ☆ | ☆☆ | ☆ | / | ☆ | 8 |
Ming-Xiong Sheng al 2017 [30] | / | ☆ | ☆ | ☆ | / | ☆ | ☆ | ☆ | 6 |
Won Sik Jang al. 2018 [31] | ☆ | ☆ | ☆ | ☆ | ☆ | ☆ | / | ☆ | 7 |
Tian Lan al. 2019[32] | ☆ | / | ☆ | ☆ | ☆ | ☆ | / | ☆ | 6 |
Nasser Simforoosh al. 2019[33] | ☆ | / | ☆ | ☆ | / | ☆ | ☆ | ☆ | 6 |
Shubin Si al. 2021[34] | ☆ | ☆ | ☆ | ☆ | ☆☆ | ☆ | / | ☆ | 8 |