Primary Outcomes: Blinded to Echinacea vs Open-Label Echinacea Groups
| Outcome | Blinded to Echinacea | Open-Label Echinacea | Between-Group Differences |
|---|---|---|---|
| SF-8 = SF-8 Health Survey; WURSS-21 = 21-item Wisconsin Upper Respiratory Symptom Survey. | |||
| a Global severity represents area-under-the-curve, with WURSS-21 scores the y-axis and illness duration the x-axis. | |||
| b Because global severity was skewed, we first transformed using Box Cox methods, then adjusted for potential confounders with a mixed general linear model, controlling for symptom duration before entry, cold severity at entry, age, sex, ethnicity, education, income, smoking status, physical and mental health (SF-8), and randomized assignment to the 3 clinician-related groups. | |||
| c Belief in echinacea (expectancy) was assessed by asking, “How effective do you think that echinacea is?” Participants responded by marking a visual analogue scale, which ranged from 0 (totally ineffective) to 100 (extremely effective). | |||
| Sample size (protocol completers), n | 183 | 181 | – |
| Illness duration, mean (95% CI), d | 6.34 (5.86 to 6.83) | 6.76 (6.24 to 7.27) | 0.42 (−0.28 to 1.12) |
| Illness duration, median (95% CI), d | 6.04 (5.30 to 6.53) | 6.16 (5.31 to 6.60) | 0.12 (−0.82 to 1.05) |
| Global severity score, mean (95% CI)a | 236 (210 to 263) | 258 (226 to 289) | 22.0 (−18.9 to 62.9) |
| Global severity score, median (95% CI)a | 193 (163 to 218) | 195 (169 to 213) | 2.00 (−34.0 to 37.5) |
| Transformed and adjusted global severity score (95% CI)b | 10.1 (9.7 to 10.4) | 10.1 (9.7 to 10.5) | 0.08 (−0.37 to 0.73) |
| Participants who rated echinacea’s effectiveness >50c | |||
| Subsample size, n | 33 | 30 | – |
| Illness duration, mean (95% CI), d | 7.10 (5.80 to 8.40) | 7.07 (5.85 to 8.29) | −0.03 (−1.78 to 1.72) |
| Illness duration, median (95% CI), d | 6.45 (4.32 to 8.40) | 6.51 (5.50 to 8.92) | 0.06 (−2.46 to 2.58) |
| Global severity score, mean (95% CI)a | 275 (179 to 370) | 264 (198 to 330) | −11.0 (−126.6 to 104.6) |
| Global severity score, median (95% CI)a | 202 (125 to 264) | 243 (172 to 303) | 41.0 (−50.2 to 130.6) |
| Transformed and adjusted global severity score (95% CI)b | 10.1 (9.1 to 11.2) | 10.4 (9.5 to 11.3) | 0.30 (−1.10 to 1.70) |