Secondary Outcomes and Side Effects, by Study Group
| Outcome | No Pill | Blinded to Placebo | Blinded to Echinacea | Open-Label Echinacea |
|---|---|---|---|---|
| IL-8 = interleukin 8; PSS-4 = Cohen’s Perceived Stress Scale-4; SF-8 = SF-8 Health Survey. | ||||
| a Data for IL-8 concentration and neutrophil count reflect median change in from baseline (day 1) to day 3. | ||||
| b Mean rank difference and geometric mean are shown for IL-8 concentration and neutrophil count because these measures were highly skewed and did not satisfy statistical assumptions of normality. | ||||
| c Mean values from day 3. | ||||
| d Side effects were assessed at exit by asking whether the participant had these at any time during the cold. | ||||
| e Comparing those reporting headache in the no-pill group with those in the other 3 groups combined yields χ2 of 22.3, which with 1 df is statistically significant at P <.001. Using χ2 to test dichotomous outcomes and the F test to test continuous outcomes, headache was the only between-group difference that reached P ≤.01. | ||||
| f 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). | ||||
| IL-8 concentration change, median, pg/mL (95% CI)a | 30 (2–89) | 39 (12–106) | 58 (18–105) | 70 (18–134) |
| IL-8 concentration rank difference, mean, pg/mLb | 322 | 333 | 330 | 358 |
| IL-8 concentration geometric change, mean, pg/mL (95% CI)b | 211 (140–316) | 208 (141–308) | 222 (159–311) | 267 (181–393) |
| Neutrophil count change, median, na | 1.0 | 1.0 | 2.0 | 1.0 |
| Neutrophil count difference, mean rank, nb | 312 | 322 | 327 | 345 |
| Neutrophil count, geometric change, mean (95% CI), nb | 20.1 (15–29) | 27.1 (19–40) | 21.5 (15–31) | 26.9 (18–40) |
| SF-8 physical health score, n (95% CI)c | 48.0 (47.1–49.0) | 46.9 (45.9–48.0) | 47.3 (46.2–48.4) | 47.7 (46.8–48.6) |
| SF-8 mental health score, mean (95% CI)c | 43.8 (42.3–45.3) | 42.5 (41.0–43.9) | 44.4 (43.1–45.7) | 43.7 (42.2–45.2) |
| EuroQol Feeling Thermometer score, mean (95% CI)c | 59.0 (56.0–61.9) | 60.8 (57.5–64.0) | 63.1 (60.3–65.9) | 62.0 (59.2–64.8) |
| PSS-4 stress score, mean (95% CI)c | 11.7 (11.2–12.1) | 11.4 (11.0–11.9) | 11.5 (11.1–12.0) | 11.5 (11.1–11.9) |
| Side effects, % (95% CI)d | ||||
| Bad taste | NA | 9.1 (7.2–16.8) | 12.4 (7.6–17.3) | 8.9 (4.7–13.1) |
| Diarrhea | 5.4 (2.0–8.9) | 12.0 (7.2–16.8) | 9.6 (5.3–13.9) | 9.4 (5.2–13.7) |
| Headachee | 62.1 (54.7–69.4) | 49.1 (41.7–56.5) | 46.3 (39.0–53.7) | 47.8 (40.5–55.1) |
| Nausea | 10.2 (5.6–14.9) | 12.6 (7.7–17.5) | 15.8 (10.4–21.2) | 6.7 (3.0–10.3) |
| Rash | 1.8 (0.0–3.8) | 1.1 (0.0–2.7) | 1.1 (0.0–2.7) | 1.7 (0.0–3.5) |
| Stomach upset | 16.3 (10.7–21.9) | 12.0 (7.2–16.8) | 14.7 (9.5–19.9) | 13.3 (8.4–18.3) |
| Participants who rated echinacea’s effectiveness >50f | ||||
| Subsample size, n | 32 | 25 | 33 | 30 |
| IL-8 concentration change, median, pg/mL (95% CI)a | 43 (17–57) | 66 (47–81) | 64 (27–72) | 66 (36–93) |
| IL-8 concentration geometric change, mean, pg/mL (95% CI)b | 28 (18–43) | 55 (41–75) | 42 (29–62) | 56 (45–70) |
| Neutrophil count change, median, na | 40 (20–59) | 47 (26–76) | 63 (33–73) | 67 (39–87) |
| Neutrophil count, geometric change, mean (95% CI), nb | 28 (17–45) | 38 (26–57) | 48 (36–64) | 56 (44–70) |