Table 1.
Trends in the Prevalence of Research Study Design Over the 20-Year Period.
| Study type | 1993 (%) n = 167 | 1998 (%) n = 216 | 2003 (%) n = 181 | 2008 (%) n = 191 | 2013 (%) n = 217 | Total (%) N = 972 |
|---|---|---|---|---|---|---|
| Randomized controlled trials | 0 (0) | 3 (1.4) | 9 (4.9) | 11 (5.7) | 6 (2.7) | 29 (2.9) |
| Systematic review/meta-analysis | 1 (0.6) | 0 (0) | 1 (0.5) | 2 (1.0) | 9 (4.1) | 13 (1.3) |
| Prospective cohort | 10 (5.9) | 16 (7.4) | 19 (10.5) | 25 (13.0) | 25 (11.5) | 96 (9.8) |
| Retrospective cohort | 17 (10.2) | 12 (5.5) | 15 (8.3) | 26 (13.6) | 29 (13.3) | 99 (10.1) |
| Case-control | 5 (2.9) | 4 (2.4) | 5 (2.7) | 2 (1.0) | 6 (2.7) | 22 (2.2) |
| Case series | 90 (53.9) | 105 (48.6) | 95 (52.4) | 82 (42.9) | 91 (41.9) | 463 (47.6) |
| Case reports | 44 (26.3) | 76 (35.2) | 37 (20.4) | 42 (21.9) | 51 (23.5) | 250 (25.7) |