Influenza A H1N1: Retrospective Analysis of PCR Confirmed Cases of H1N1 Infections in Styria - Risk Factors, Clinical Features and Outcome.

Study Overview
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Brief Summary
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This retrospective study will analyse all PCR-proven H1N1 cases from the influenza season 2009/2010 treated within the styrian LKH hospital network. For this purpose all PCR-positive case files are reviewed in Medocs (electronic patients database) and data regarding clinical presentation, laboratory and radiological findings, treatment, outcome and preexisting underlying chronic illnesses will be systematically collected. In a second step the same data collection will be performed in a group of PCR-negative patients, which were tested during the influenza season 2009/2010 for influenza-like illness. The data from the PCR-positive group will be compared to the data from the PCR-negative group. We expect significant differences between the proven and unproven group regarding the primary presentation at hospital. Based on these results a clinical score will be developed. This score should improve H1N1 case identification in emergency departments, even if specific diagnostic test are negative (rapid antigen testing) or still pending (PCR), reduce the number of missed hospitalized H1N1 infection and optimize the decision making process in emergency departments regarding which patient has to be admitted with infection control measures and which not, and as infection control measures are expensive (face masks, gloves) and limited (isolation room), such a score should also reduce unnecessary expense. To evaluate the sensitivity and specificity of the score a prospective study will follow in the influenza season 2010/2011.

Official Title
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Influenza A H1N1: Retrospective Analysis of PCR Confirmed Cases of H1N1 Infections in Styria - Risk Factors, Clinical Features and Outcome. Development of a Clinical Score for Suspected H1N1 Infection.

Conditions
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Clinically Suspected H1N1 Infection

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Inclusion criteria: All patients tested for influenza illness by PCR of respiratory tract specimens at the Institute of Hygiene, Karl-Franzens-University Graz, and at the Institute for Hospital Hygiene and Microbiology, KAGES Graz. Stratification according to the following definition: PCR-negative influenza-like illness (ILI) is defined as febrile illness tested by PCR for the presence of influenza infection but finally not proved as influenza infection. Influenza illness is defined as febrile illness confirmed by positive PCR as true influenza infection. Exclusion Criteria: NONE
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| positive<br>Patients with clinically suspected H1N1 infection confirmed by positive H1N1 PCR | |
| negative<br>Patients with clinically suspected H1N1 infection and negative H1N1 PCR | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| clinical presentation of H1N1 compared to other viral infections |  | 2 years |