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Included studies by design and date of publication
| Total | Case report/series | Observational: cross sectional | Observational: case controlled | Observational: cohort | |
|---|---|---|---|---|---|
| 1988 or earlier | 21 (20%) | 19 (90%) | 1 (5%) | 1 (5%) | 0 |
| 1989–1998 | 16 (15%) | 10 (63%) | 5 (31%) | 1 (6%) | 0 |
| 1999–2008 | 20 (19%) | 11 (55%) | 4 (20%) | 5 (25%) | 0 |
| 2009–2019 | 48 (46%) | 22 (46%) | 19 (40%) | 5 (10%) | 2 (4%) |
