Reporting of stepped-wedge cluster randomised trial sample size elements according to the proposed modification to the Cluster 2012 extension for cluster randomised trials
| All reports N=60 | 1987–2012 N=28 | 2013–2014 N=32 | Absolute difference (95% CI) | p Value | |
|---|---|---|---|---|---|
| Number of steps | |||||
| Explicitly reported | 54 (90.0) | 23 (82.1) | 31 (96.9) | 14.7 (−0.7 to 30.1) | 0.058 |
| Reported or deducible | 59 (98.3) | 27 (96.4) | 32 (100.0) | 3.6 (−3.3 to 10.4) | 0.281 |
| Number clusters randomised per step | |||||
| Reported | 56 (93.3) | 25 (89.3) | 31 (96.9) | 7.6 (−5.4 to 20.5) | 0.240 |
| Schematic representation | |||||
| Reported | 46 (76.7) | 20 (71.4) | 26 (81.3) | 9.8 (−11.7 to 31.3) | 0.370 |
| Design type (ie, cross-sectional/cohort) | |||||
| Explicitly reported | 16 (26.7) | 6 (21.4) | 10 (31.3) | 9.8 (−12.3 to 31.9) | 0.391 |
| Reported or deducible | 43 (71.7) | 19 (67.9) | 24 (75.0) | 7.1 (−15.8 to 30.0) | 0.540 |
| Clarity of cluster size† | |||||
| Total cluster size reported | 17 (28.3) | 8 (28.6) | 9 (28.1) | −0.4 (−23.3 to 22.4) | 0.969 |
| Cluster size per measurement period reported | 25 (41.7) | 10 (35.7) | 15 (46.9) | 11.2 (−13.6 to 35.9) | 0.382 |
| Unclear/not reported | 29 (48.3) | 15 (53.6) | 14 (43.8) | −9.8 (−35.1 to 15.4) | 0.448 |
Values are numbers (percentages) unless stated otherwise.
p Value is for the comparison of 1987–2012 publications and 2013–2014 publications using a χ2 test for proportions.
†Some studies reported both total cluster size and cluster size per measurement period.