Table 6.
Association between the trial retention rate (% of randomised participants with valid primary outcome data for analysis) and trial characteristics
| Characteristic | n | Median | IQR | p Value |
|---|---|---|---|---|
| Setting | ||||
| Hospital | 81 | 92.4 | 81.7–99.1 | |
| General practice | 20 | 85.6 | 77.4–91.0 | |
| Mixed | 25 | 90.0 | 84.8–97.4 | |
| Community | 16 | 85.4 | 79.1–96.1 | 0.019*† |
| Other | 8 | 99.4 | 98.8–100.0 | |
| Arms | ||||
| 2 | 100 | 0.90 | 0.82–0.98 | |
| 3 | 30 | 0.89 | 0.79–0.97 | |
| 4+ | 20 | 0.92 | 0.83–0.97 | 0.747† |
| Control type | ||||
| Placebo | 30 | 90.0 | 88.7–99.4 | |
| Active | 120 | 89.9 | 81.0–97.4 | 0.166‡ |
| Final target recruitment | ||||
| ≤200 | 17 | 93.7 | 87.6–98.3 | |
| 201–400 | 49 | 89.2 | 79.8–96.8 | <0.001§ |
| 401–600 | 27 | 86.7 | 72.2–100.0 | |
| 601–800 | 13 | 86.3 | 83.2–89.9 | |
| >800 | 44 | 94.0 | 76.4, 99.4 | |
| Total recruitment | ||||
| ≤200 | 23 | 94.7 | 86.4–100.0 | |
| 201–400 | 48 | 89.1 | 79.3–96.4 | <0.001§ |
| 401–600 | 28 | 85.7 | 81.7–92.5 | |
| 601–800 | 12 | 89.9 | 88.5–94.6 | |
| >800 | 39 | 94.0 | 77.8–99.3 | |
| Timing of final follow-up | ||||
| <1 month | 9 | 99.3 | 77.4–100.0 | |
| 1–6 months | 41 | 94.6 | 84.8–100.0 | 0.693§ |
| 6–18 months | 62 | 86.2 | 75.1–96.8 | |
| >18 months | 33 | 89.2 | 85.6–95.4 | |
*The category ‘other’ was not included in Kruskal-Wallis test.
†p Values are reported from a Kruskal-Wallis test.
‡p Values are reported from a Wilcoxon rank sum test.
§p Values are reported from a nonparametric test of trend (Cuzick).