Table 1. General Characteristics of the Studies Using Case-Crossover and/or Self-Controlled Case Series Designs.
| Case-Crossover(n = 50) | Self-Controlled Case Series(n = 45) | All Articles(n = 93)a | |
| No. (%) | No. (%) | No. (%) | |
| Designs | 50 (100) | 45 (100) | 93 (100)a |
| Several designs were used | 24 (48) | 17 (38) | 39 (42) a |
| Additional case-only study | 2 SCCS | 2 CC | 2 (2) a |
| Additional case-control study | 13 (26) | 6 (13) | 19 (20) |
| Additional cohort study | 7 (14) | 5 (11) | 12 (13) |
| Additional case-time-control study coupled to CC design | 5 (10) | 5 (5) | |
| Additional ecological study | 2 (4) | 3 (7) | 5 (5) |
| Rationale for the use of a case-only design | 43 (86) | 34 (76) | 75 (81) a |
| To limit biasb | 30 (60) | 23 (51) | 51 (55) a |
| Practical issuesc | 21 (42) | 19 (42) | 38 (41) a |
| Justification related to event or exposure characteristics | 25 (50) | 8 (18) | 33 (35) |
a
Two reports used both CC and SCCS.
b
e.g.: bias due to fixed-confounders.
c
e.g.: suitable database, no representative control group available, necessity of easy, rapid, simple design.