Risk factor analysis for fatal outcome in ICU admitted cases with confirmed influenza infection

1. European Centre for Disease Prevention and Control
BACKGROUND
OBJECTIVE
RESULTS
CONCLUSIONS
ACKNOWLEDGEMENT
European Centre for Disease Prevention and Control (ECDC), Stockholm, Sweden
Cornelia Adlhoch, Joana Gomes Dias, and Pasi Penttinen on behalf of the reporting countries
Risk factors for fatal outcome in flu cases
admitted to ICU, 11 EU countries, 2009–2016
Cornelia.Adlhoch@ecdc.europa.eu
Fatal outcomes related to influenza infection are important indicators for the
severity of seasonal epidemics and targeted by vaccination strategies.
Of 16,081 confirmed influenza cases reported to be admitted to ICU over
seven influenza seasons, 2,279 cases reported from 11 countries and with
information on age, outcome, pre-existing conditions, complications and
vaccination status were included in the analysis. Of those, 621 died (Figures
1 and 2).
Our aim was to investigate risk factors associated with fatal outcome in
confirmed influenza cases admitted to intensive care units (ICU) over seven
influenza seasons.
In our study influenza vaccination was not associated with significantly
decreased risk of death in ICU patients, however, vaccination status was only
known for a minority of hospitalized cases. Age, cancer, HIV infection,
chronic kidney and liver disease as well as infection with influenza A were
confirmed as risk factors for fatal outcome in patients admitted to ICU in EU
countries.
Finland: Outi Lyytikäinen, Niina Ikonen, Satu Murtopuro, Anu Haveri; France: Blanchon Thierry,
Clement Turbelin, Emmanuel Belchior, Isabelle Bonmarin, Sylvie Behillil, Bruno Lina, Martine Valette,
Sylvie van der Werf, Vincent Enouf; Ireland: Lisa Domegan, Allison Waters, Joan O’Donnell, Margaret
Duffy, Suzie Coughlan, Derval Igoe; Malta: Christopher Barbara, Jackie Maistre Melillo, Tanya Melillo,
Graziella Zahra; Netherlands: Mariette Hooiveld, Anne Teirlinck, Adam Meijer, Frederika Dijkstra, Gé
Donker, Guus Rimmelzwaan, Marit de Lange; Portugal: Ana Paula Rodrigues , Helena Rebelo De
Andrade, Raquel Moreira Guiomar; Romania: Emilia Lupulescu, Florin Popovici; Slovak Republic:
Edita Staronová; Spain: Amparo Larrauri, Francisco Pozo, Inmaculada Casas, Leonardo Raul Ortiz De
Lejarazu, Tomas Pumarola, Tomas Vega.
ECDC: Eeva Broberg and René Snacken
METHODS
The European Centre for Disease Prevention and Control collects case-based
data on hospitalised confirmed cases of influenza from EU/EEA Member
States on a weekly basis. We studied cases admitted to ICUs and reported
during the consecutive influenza seasons 2009 to 2016 between week 40
and 20 in the subsequent year. We described them by age, virus type and
subtype and outcome. We analysed the association of age, underlying
condition, complications, virus type/subtype and vaccination status with fatal
outcome by multivariable logistic regression (inclusion criteria: p<0.05 in the
univariable analysis).
RESULTS
Independent factors associated with increased likelihood of fatal outcome
were increasing age, cancer, HIV infection, kidney and liver disease, sepsis
as well as infection with A(H1N1)pdm09 or A(H3N2). Eighteen percent of the
fatal cases had been vaccinated, but vaccination was not associated with
outcome in neither the uni- nor the multivariable analysis (Table).
Fatal cases
N= 621
Recovered cases
N=1 658
Adjusted for season and country
Factors n % n % Odds ratio (95%CI)
Male 355 57 903 55 1.0 (0.8-1.2)
Age
0–9 yrs 23 4 129 8
10–19 yrs 10 2 60 4 1.0 (0.4-2.4)
20–29 yrs 26 4 100 6 1.6 (0.8-3.2)
30–39 yrs 53 9 156 9 1.9 (1.1-3.4)
40–49 yrs 73 12 255 15 1.4 (0.8-2.5)
50–59 yrs 158 25 348 21 2.6 (1.5-4.4)
60–69 yrs 141 23 324 20 2.5 (1.5-4.3)
70–79 yrs 99 16 206 12 3.1 (1.8-5.5)
80+ yrs 38 6 80 5 3.6 (1.9-7.0)
Underlying conditions
Asthma 12 2 53 3
Cancer 28 5 35 2 2.7 (1.5-4.9)
Diabetes 70 11 186 11
Heart disease 87 14 128 8 1.3 (0.9-1.9)
HIV 65 10 79 5 2.7 (1.8-4.0)
Kidney disease 30 5 44 3 1.8 (1.1-3.1)
Liver disease 25 4 41 2 2.2 (1.2-3.9)
Lung disease 92 15 251 15
Neurocognitive 3 0 10 1
Neuromuscular disorders 6 1 24 1
Obesity 63 10 215 13
Morbid obesity 27 4 67 4
Pregnancy 15 2 70 4 0.9 (0.5-1.7)
Complications
Sepsis 58 9 46 3 5.5 (3.4-8.9)
ARDS 347 56 873 53
Pneumonia 212 34 592 36
Virus (sub)type
B 62 10 244 15
A(H1N1)pdm09 474 76 1168 70 2.1 (1.5-3.1)
A(H3N2) 85 14 246 15 1.5 (1.0-2.3)*
Vaccination status
Vaccinated 113 18 314 19 1.0 (0.8-1.4)
Table: Risk factors for fatal outcome
Figure 2: Cases in ICU by age-group, virus (sub)type and outcome, seasons 2009/2010 – 2015/2016
Figure 1: Flow chart of cases included in the analysis
Confirmed influenza cases admitted to ICU seasons 2009/10–2015/16 (weeks 20-40)
N= 16 081
Known age
N= 8 424
Known preconditions and complications
N= 3 842
Known vaccination status
N= 2 497
Known outcome
N= 2 279
Known virus type and influenza A subtype determined
N= 11 085
Dead
N=621
Alive
N=1 658
* 95%CI: 1.002065–2.296429 P=0.049