Table 2 Comparison of patients with suspected and unsuspected influenza

Demographic data

   Age (years) (median, IQR)

53, 42-66

69, 60-79

0.008

   Male sex

11 (68.8)

9 (60)

0.71

Underlying conditions

   COPD

7 (43.8)

7 (46.7)

1

   Immunosuppression

3 (18.8)

2 (13.3)

1

   Charlson score

4.5, 2.2-7

6, 3-9

0.26

   Influenza vaccination

4 (25)

3 (20)

1

Type of ICU

   Medical

15 (93.8)

6 (40)

0.002

   Surgical

1 (6.3)

9 (60)

Reason for admission to the ICU

   Severe respiratory failure

11 (68.8)

3 (20)

0.002

   Surgery

1 (6.3)

9 (60)

   Cardiac arrest

3 (18.8)

1 (6.7)

   Other

1 (6.3)

2 (13.3)

   APACHE II score

15.5, 12.5-17.5

14, 11-17

0.40

Characteristics of influenza

   Days of symptoms before diagnosis^a

3, 1-6.7

5, 0-9

0.92

   Days of ICU stay before diagnosis^a

1, 0-1

4, 1-17

0.01

   Days of hospital stay before diagnosis^a

2.50, 1-5.75

15, 5-22

0.008

   Hospital acquired

3 (18.8)

10 (66.7)

0.01

   Fever

11 (68.8)

11 (73.3)

1

   Cough

15 (93.8)

8 (53.3)

0.01

   Dyspnea

13 (81.3)

11 (73.3)

0.68

   Pneumonia

15 (93.8)

8 (53.3)

0.01

   Localized infiltrate on chest radiograph

1 (6.3)

6 (40)

0.04

   Viral load at diagnosis (median, IQR)

2.37, 1.10-5.42

1.4, 0.23-1.97

0.09

   Days to antiviral treatment^a

2, 2-6

9, 4.5-18

0.02

   Co-infection

3 (18.8)

5 (33.3)

0.43

Outcome

   Septic shock

8 (50)

5 (33.3)

0.47

   ARDS

12 (75)

4 (26.7)

0.01

   30-day mortality

6 (37.5)

3 (20)

0.43

   Days of ICU stay (median, IQR)

11, 4-33

27, 8-50

0.21

   Days of hospital stay (median, IQR)

39, 4-46

66, 30-90

0.06