Results of Cox Regression Analysis for Interactions Between Prognostic Variables and Treatment Group*
| Interaction Term† | Hazard Ratio | 95% CI | P Value |
|---|---|---|---|
| CI = confidence interval. | |||
| * The original trial13 had 2 treatment groups: antibiotics and placebo. A significant interaction would mean that the influence of the prognostic variable on the course of illness depends on whether the patient is treated with antibiotics or placebo. | |||
| † Variables included in the multivariate model: prognostic variable + treatment group + prognostic variable × treatment group. | |||
| ‡ Graphically illustrated in Figures 3 and 4. | |||
| § n = 218. | |||
| Age (>37 years) × treatment | 1.04 | 0.62–1.73 | .79 |
| Sex × treatment | 1.06 | 0.64–1.76 | .69 |
| Purulent rhinorrhea × treatment | 1.11 | 0.67–1.84 | .68 |
| Postnasal drip × treatment | 1.01 | 0.61–1.67 | .98 |
| Temperature ≥37.5°C × treatment | 1.12 | 0.55–2.29 | .75 |
| Complaints ≥7 days × treatment | 1.10 | 0.66–1.83 | .71 |
| Biphasic illness × treatment | 1.00 | 0.60–1.67 | .97 |
| Pain on bending × treatment | 1.10 | 0.65–1.85 | .73 |
| Unilateral facial pain × treatment | 1.05 | 0.63–1.74 | .85 |
| Pain in upper teeth × treatment | 1.31 | 0.68–2.52 | .43 |
| Fatigue × treatment | 0.91 | 0.54–1.51 | .71 |
| Reduced productivity × treatment | 1.22 | 0.74–2.01 | .44 |
| General feeling of illness × treatment‡ | 0.97 | 0.58–1.61 | .91 |
| Abnormal radiograph§ × treatment | 1.25 | 0.69–2.25 | .47 |
| Clinical sum score × treatment‡ | 1.27 | 0.77–2.09 | .36 |