Table 3.

Results of Cox Regression Analysis for Interactions Between Prognostic Variables and Treatment Group*

Interaction TermHazard Ratio95% CIP 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) × treatment1.040.62–1.73.79
Sex × treatment1.060.64–1.76.69
Purulent rhinorrhea × treatment1.110.67–1.84.68
Postnasal drip × treatment1.010.61–1.67.98
Temperature ≥37.5°C × treatment1.120.55–2.29.75
Complaints ≥7 days × treatment1.100.66–1.83.71
Biphasic illness × treatment1.000.60–1.67.97
Pain on bending × treatment1.100.65–1.85.73
Unilateral facial pain × treatment1.050.63–1.74.85
Pain in upper teeth × treatment1.310.68–2.52.43
Fatigue × treatment0.910.54–1.51.71
Reduced productivity × treatment1.220.74–2.01.44
General feeling of illness × treatment0.970.58–1.61.91
Abnormal radiograph§ × treatment1.250.69–2.25.47
Clinical sum score × treatment1.270.77–2.09.36