Table 4.

C-reactive protein (CRP) and other factors to differentiate between influenza A and B vs other causes of influenza-like illness (ILI).

	influenza Aa			influenza Bb
	Adjusted ORc	95% CI	p Value	Adjusted ORd	95% CI	p Value
CRP (mg/L)e	1.0	0.91–1.2	.61	0.42	0.25–0.70	<.001
Increasing age in years	1.0	0.98–1.0	.84	0.99	0.97–1.0	.52
Female gender	1.4	0.78–2.6	.25	0.53	0.21–1.3	.18
Duration ref <24 h	1.0			1.0
Duration 24–48 h	0.85	0.41–1.7	.65	0.43	0.13–1.4	.16
Duration 48–72 h	0.71	0.34–1.5	.36	2.2	0.83–6.1	.11
Increasing body temperature of one degree Celsius	1.1	0.76–1.6	.60	1.3	0.72–2.3	.40
Increasing pulse of one beat	1.0	0.98–1.0	.56	0.97	0.94–1.0	.22
Your health todayf	0.99	0.97–1.0	.091	1.0	0.98–1.0	.61
Perceived feverg	2.1	0.82–5.7	.12	1.6	0.42–6.2	.48
Running/congested noseg	1.2	0.63–2.2	.63	0.69	0.29–1.6	.40
Sore throatg	0.53	0.29–0.97	.038	0.79	0.33–1.9	.59
Headacheg	0.85	0.41–1.7	.65	2.8	0.87–9.3	.085
Coughg	1.4	0.75–2.7	.28	3.4	1.2–9.1	.017
Shortness of breathg	1.3	0.52–3.0	.61	0.16	0.028–0.89	.036
Muscle ache and painsg	1.6	0.82–3.2	.17	0.94	0.37–2.4	.89
Sweats or chillsg	1.3	0.61–2.6	.52	0.75	0.25–2.3	.62
Low energy/tiredg	0.48	0.18–1.3	.14	1.5	0.34–6.7	.59
Not sleeping wellg	1.2	0.63–2.3	.56	0.57	0.22–1.5	.25
Dizzinessg	0.54	0.25–1.2	.12	4.3	1.3–14	.014
Feeling generally unwellg	1.8	0.62–5.0	.28	0.81	0.19–3.4	.77

^aInfluenza A versus all other etiologies (influenza B and not influenza).

^bInfluenza B versus all other etiologies (influenza A and not influenza).

^c224 included in analysis (104 with influenza A and 120 with other etiology). Nagelkerke R square 0.14. Area under the curve (95% CI; p value): 0.68 (0.61–0.75; <.001).

^d224 patients included in analysis (43 with influenza B and 181 with other etiology). Nagelkerke R square 0.39. Area under the curve (95% CI; p value): 0.86 (0.81–0.92; <.001).

^eIncremental steps of ten.

^fEQ-VAS EuroQol Group: 0 = worst possible health, 100 = best possible health. Odds ratio given for an increase of one step.

^gModerate or major symptoms.

Statistically significant findings at 5% level are bold.