An evaluation of a hospital influenza surveillance program using Emergency Department coding and laboratory data

Interest in influenza management has been increasing since 2003 with the emergence of influenza strains, such as avian H5N1, with pandemic potential. Within Victoria, influenza surveillance data is collected through community presentation; however, assessment at Melbourne Health (MH) indicated there was little data about the number of influenza-like illnesses (ILI) and influenza presentations and admissions through the health service. This study, conducted between 2006 and 2008, aimed to develop a real-time process, using syndromic (monitoring of selected International Classification of Disease (ICD-10) codes to the Emergency Department (ED)) and laboratory data sources (requests for respiratory polymerase chain reaction (PCR) tests), to monitor ILI presentations and admissions. The results obtained indicated that the syndromic surveillance of a range of ICD-10 codes was not a sensitive method to identify patients admitted with an ILI. Each year, of the patients admitted with the selected syndromic code, only 11% were diagnosed with influenza. Only one code, J11.1 demonstrated some sensitivity and specificity of a final diagnosis of influenza. The other selected ICD-10 codes were likely to have a diagnosis unrelated to influenza. Monitoring of respiratory PCR tests showed that a range of ICD-10 codes were used to code patients presenting toEDas well as identifying that a significant number of patients confirmed to have influenza did not present to the organisation via the ED. As a result of the project, a combination of syndromic and laboratory surveillance was utilised during the 2009, H1N1 influenza pandemic to provide information on influenza presentations and admissions to the organisation.