Table 1 Patients characteristics at enrolment
|  | 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%) |  |  |