Table 2 Quality of the included studies
No | References | Selection | Compatibility | Exposure | Total score (7) | Rating (High, moderate, low quality) | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Is the case definition adequate? | Representativeness of the cases | Selection of controls | Definition of controls | Ascertainment of exposure | Same method of ascertainment for cases and controls | Non-response rate | |||||
1 | Abah and Udoidang 2019 [30] |
|
| NA | NA |
|
|
|
| 7 | High |
2 | Abah et al. 2019 [29] |
| Â | NA | NA |
|
|
|
| 6 | High |
3 | Adeleke et al. 2013 [31] |
| Â | NA | NA |
|
|
|
| 6 | High |
4 | Aernan et al. 2011 [10] |
|
| NA | NA |
|
|
|
| 7 | High |
5 | Afolabi et al. 2018 [15] |
|
| NA | NA |
|
|
|
| 7 | High |
6 | Anabire et al. 2019 [23] |
| Â | NA | NA |
|
|
|
| 6 | High |
7 | Andrade et al. 2011 [9] |
|
| NA | NA |
|
|
|
| 7 | High |
8 | Braga et al. 2005 [17] |
|
| NA | NA |
|
|
|
| 7 | High |
9 | Braga et al. 2006 [32] |
|
| NA | NA |
|
|
|
| 7 | High |
10 | Cruz et al. 2019 [14] |
| Â | NA | NA |
|
|
|
| 6 | High |
11 | Dabo et al. 2015 [16] |
|
| NA | NA |
|
|
|
| 7 | High |
12 | Freimanis et al. 2012 [8] |
| Â | NA | NA |
|
|
|
| 6 | High |
13 | Gadia et al. 2017 [24] |
| Â | NA | NA |
|
|
|
| 6 | High |
14 | Helegbe et al. 2018 [25] |
| Â | NA | NA |
|
|
|
| 6 | High |
15 | Kolawole and Kana 2018 [33] |
|
| NA | NA |
|
|
|
| 7 | High |
16 | Omalu et al. 2012 [34] |
| Â | NA | NA |
|
|
|
| 6 | High |
17 | Oyeyemi et al. 2015 [26] |
|
| NA | NA |
|
|
|
| 7 | High |
18 | Scotto and Fazio 2018 [27] |
|
| NA | NA |
|
|
|
| 7 | High |
19 | Sharif et al. 2015 [28] |
|
| NA | NA |
|
|
|
| 7 | High |
20 | Thursz et al. 1995 [11] |
| Â | NA | NA |
|
|
|
| 6 | High |
21 | Wokem and Amacree 2018 [35] |
|
| NA | NA |
|
|
|
| 7 | High |
22 | Yohanna et al. 2016 [36] |
|
| NA | NA |
|
|
|
| 7 | High |
-
A star system developed by the Newcastle–Ottawa Scale (NOS) for assessing the quality of non-randomized studies in meta-analyses, which consists of three domains including selection, comparability, and outcomes. A maximum of six stars (the highest quality) for the cross-sectional and retrospective studies was modified from the NOS for assessing the quality of the included studies. Any study rated ≥ 5 stars was considered a high-quality study - NA Not assessed