When should a diagnosis of influenza be considered in adults requiring intensive care unit admission? Results of population-based active surveillance in Toronto

Table 2 Characteristics of influenza-positive patients admitted to ICUs^a

Characteristics	Influenza A (seasonal) (n= 55)	Influenza B (n= 42)	Pandemic H1N1 (n= 29)	P value
Male gender, n (%)	26 (47.3)	24 (58.5)	19 (65.5)	0.24
Median age, years (IQR)	77.6 (63.7 to 83.6)	73.3 (57.2 to 80.8)	50.1 (43.6 to 61.9)	<0.001
18 to 44, n (%)	4 (7.3)	2 (4.8)	9 (31.0)	0.001
45 to 64, n (%)	10 (18.2)	14 (33.3)	14 (48.3)	0.015
65 to 84, n (%)	34 (61.8)	20 (47.6)	6 (20.7)	0.002
≥85, n (%)	7 (12.7)	6 (14.3)	0 (0.0)	0.09
Median admission temperature, °C (IQR)	37.1 (36.4 to 37.7)	36.7 (36.1 to 37.8)	37.7 (37.3 to 38.2)	0.004
>38.0°C, n (%)	13 (23.6)	10 (23.8)	11 (37.9)	0.32
Respiratory symptoms, n (%)	51 (92.7)	36 (87.8)	27 (96.4)	0.44
Admission diagnosis
Respiratory infection^b	18 (32.7)	16 (38.0)	17 (58.6)	0.06
Respiratory failure^c	11 (20.0)	11 (26.2)	3 (10.3)	0.26
Sepsis	3 (5.5)	1 (2.4)	2 (6.9)	0.65
Cardiac	16 (29.1)	10 (23.8)	3 (10.3)	0.15

^aIQR: interquartile range; ^b'pneumonia' and 'other respiratory infection'; ^c'chronic obstructive pulmonary disease exacerbation', 'asthma exacerbation' and 'respiratory failure'.

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