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Table 1 Patients characteristics at enrolment

From: Influenza in Malaysian adult patients hospitalized with community-acquired pneumonia, acute exacerbation of chronic obstructive pulmonary disease or asthma: a multicenter, active surveillance study

  Influenza-positive
(N = 114)
Influenza-negative (N = 992) Total
(N = 1106)
χ2(df) Or t (df) p-value#
Enrolment site, n (%)
 HKL 28 (24.6%) 275 (27.7%) 303 (27.4%) 1.495 (2) 0.474
 UMMC 28 (24.6%) 272 (27.4%) 300 (27.1%)   
 UiTM 58 (50.8%) 445 (44.9%) 503 (45.5%)   
Age, years
 Median (min; max) 64 (18; 97) 63 (18; 101) 63 (18; 101) N/A N/A
 Mean (SD) 59.1 (18.1) 59.6 (17.6) 59.6 (17.6) 0.315 (1104) 0.753
Age group, years
 18–24 40 (4.0%) 5 (4.4%) 45 (4.1%) 2.576 (6) 0.860
 25–34 75 (7.6%) 12 (10.5%) 87 (7.9%)   
 35–44 94 (9.5%) 12 (10.5%) 106 (9.6%)   
 45–54 118 (11.9%) 12 (10.5%) 130 (11.8%)   
 55–64 211 (21.3%) 19 (16.7%) 230 (20.8%)   
 65–74 256 (25.8%) 31 (27.2%) 287 (25.9%)   
  ≥ 75 198 (20%) 23 (20.2%) 221 (20.0%)   
Gender
 Male 46 (40.4%) 505 (50.9%) 551 (49.8%) 4.558 (1) 0.033*
 Female 68 (59.6%) 487 (49.1%) 555 (50.2%)   
Mean number of comorbidities (SD) 1.57 (1.20) 1.67 (1.01) 1.66 (1.03) 0.982 (1104) 0.326
Significant comorbidities
 No 20 (17.5%) 92 (9.3%) 112 (10.1%) 7.683 (1) 0.006*
 Yes 94 (82.5%) 900 (90.7%) 994 (89.9%)   
Type of comorbidities
Cardiovascular disease
 No 66 (57.8%) 496 (50%) 562 (50.8%) 2.550 (1) 0.110
 Yes 48 (42.1%) 496 (50%) 544 (49.2%)   
Diabetes
 No 70 (61.4%) 636 (64.1%) 706 (63.8%) 0.325 (1) 0.569
 Yes 44 (38.6%) 356 (35.9%) 400 (36.2%)   
Renal impairment
 No 100 (87.7%) 853 (86%) 953 (86.2%) 0.257 (1) 0.612
 Yes 14 (12.3%) 139 (14%) 153 (13.8%)   
Autoimmune disease
 No 105 (92.1%) 941 (94.9%) 1046 (94.6%) 1.511 (1) 0.219
 Yes 9 (7.9%) 51 (5.1%) 60 (5.4%)   
Asthma
 No 79 (69.3%) 699 (70.5%) 778 (70.3%) 0.067 (1) 0.796
 Yes 35 (30.7%) 293 (29.5%) 328 (29.7%)   
COPD
 No 93 (81.6%) 766 (77.2%) 859 (77.7%) 1.121 (1) 0.290
 Yes 21 (18.4%) 226 (22.8%) 247 (22.3%)   
Other (Liver cirrhosis, neurological disorder, HIV, chronic lung disease and malignancy)
 No 107 (93.9%) 900 (90.7%) 1007 (91.0%) 1.232 (1) 0.267
 Yes 7 (6.1%) 92 (9.3%) 99 (9.0%)   
BMI mean (SD) 26.4 (7.5) 26.1 (6.9) 26.5 (7.6) 0.462 (632) 0.670
Smoking status
 Never 78 (68.4%) 584 (59.2%) 662 (59.9%) 4.508 (2) 0.105
 Former 21 (18.4%) 199 (20.2%) 220 (19.9%)   
 Current 15 (13.2%) 204 (20.7%) 219 (19.8%)   
 Missing NA NA 5 (0.5%)   
Socio-professional category‡
 High socio-professional category 16 (14%) 117 (11.8%) 133 (12%) 3.340 (4) 0.503
 Middle socio-professional category 15 (13.2%) 112 (11.3%) 127 (11.5%)   
 Low socio-professional category 5 (4.4%) 85 (8.6%) 90 (8.1%)   
 Not working/unknown 61 (53.5%) 508 (51.2%) 569 (51.4%)   
 Retired 17 (14.9%) 170 (17.1%) 187 (16.9%)   
Diagnoses at admission
Acute exacerbation of asthma (AEBA)
 No 79 (69.3%) 700 (70.6%) 779 (70.4%) 0.079 (1) 0.779
 Yes 35 (30.7%) 292 (29.4%) 327 (29.6%)   
Acute exacerbation of COPD (AECOPD)
 No 95 (83.3%) 772 (77.8%) 867 (78.4%) 1.833 (1) 0.176
 Yes 19 (16.7%) 220 (22.2%) 239 (21.6%)   
Community-acquired pneumonia (CAP)
 No 26 (22.8%) 242 (24.4%) 268 (24.2%) 0.140 (1) 0.708
 Yes 88 (77.2%) 750 (75.6%) 838 (75.8%)   
Systemic symptoms at admission
 At least 1 systemic symptoms present      
 No 0 (0%) 3 (0.3%) 3 (0.3%)   1.000¥
 Yes 114 (100%) 989 (99.7%) 1103 (99.7%)   
Fever
 No 21 (18.4%) 293 (29.5%) 314 (28.4%) 6.214 (1) 0.013*
 Yes 93 (81.6%) 699 (70.5%) 792 (71.6%)   
Headache
 No 97 (85.1%) 842 (84.9%) 939 (84.9%) 0.003 (1) 0.953
 Yes 17 (14.9%) 150 (15.1%) 167 (15.1%)   
Malaise
 No 66 (57.9%) 492 (49.5%) 558 (50.5%) 2.816 (1) 0.093
 Yes 48 (42.1%) 500 (50.4%) 548 (49.5%)   
Myalgia
 No 95 (83.3%) 838 (84.5%) 933 (84.4%) 0.101 (1) 0.750
 Yes 19 (16.7%) 154 (15.5%) 173 (15.6%)   
Respiratory symptoms
At least 1 respiratory symptoms present
 No 0 (0%) 1 (0.1%) 1 (0.1%)   1.000¥
 Yes 114 (100%) 991 (99.9%) 1105 (99.9%)   
Cough
 No 11 (9.6%) 82 (8.3%) 93 (8.4%) 0.254 (1) 0.614
 Yes 103 (90.4%) 910 (91.7%) 1013 (91.6%)   
Dyspnea
 No 30 (26.3%) 143 (14.4%) 173 (15.6%) 10.974 (1) 0.001*
 Yes 84 (73.7%) 849 (85.6%) 933 (84.4%)   
Sore throat
 No 93 (81.6%) 805 (81.1%) 898 (81.2%) 0.012 (1) 0.911
 Yes 21 (18.4%) 187 (18.9%) 208 (18.8%)   
Enrolment month
 July 2018 4 (3.5%) 32 (3.2%) 36 (3.3%) 29.843 (13) 0.005*
 August 2018 5 (4.4%) 56 (5.6%) 61 (5.5%)   
 September 2018 1 (0.9%) 22 (2.2%) 23 (2.1%)   
 October 2018 4 (3.5%) 33 (3.3%) 37 (3.3%)   
 November 2018 14 (12.3%) 40 (4%) 54 (4.9%)   
 December 2018 7 (6.1%) 29 (2.9%) 36 (3.3%)   
 January 2019 6 (5.3%) 63 (6.4%) 69 (6.2%)   
 February 2019 14 (12.3%) 81 (8.2%) 95 (8.6%)   
 March 2019 5 (4.4%) 63 (6.4%) 68 (6.1%)   
 April 2019 7 (6.1%) 85 (8.6%) 92 (8.3%)   
 May 2019 8 (7.0%) 120 (12.1%) 128 (11.6%)   
 June 2019 18 (15.8%) 180 (18.1%) 198 (17.9%)   
 July 2019 20 (17.5%) 137 (13.8%) 157 (14.2%)   
 August 2019 1 (0.9%) 51 (5.1%) 52 (4.7%)   
≥1 hospitalization within the past 12 months
 Yes 29 (25.4%) 343 (34.6%) 372 (33.6%) 3.825 (1) 0.050
 No 85 (74.6%) 649 (65.4%) 734 (66.4%)   
≥1 consultation within the past 3 months
 Yes 32 (28.1%) 352 (35.5%) 384 (34.7%) 2.480 (1) 0.115
 No 82 (71.9%) 640 (64.5%) 734 (66.4%)   
Flu Vaccination within past 12 months and more than 14 days
 Yes 2 (1.8%) 20 (2%) 22 (2%) 0.036 (1) 0.850¥
 No or unclear 112 (98.2%) 972 (98%) 1084 (98%)   
  1. †Comorbidities that involve organ dysfunction are considered as significant comorbidities; ‡Socio-professional categories are defined in Additional file 1; #Chi-square test (unless otherwise indicated); ¥Fisher’s exact test; *p-value < 0.05
  2. HKL, Kuala Lumpur General Hospital; NA, not available; UMMC, University of Malaya Medical Centre; UiTM, Selayang Hospital