Use of Saliva in the Detection of Influenza Viruses at the Accident and Emergency Department During an Influenza Epidemic

Abstract

Nasopharyngeal specimen has been the preferred specimen type for respiratory virus detection. However, the collection of nasopharyngeal specimen is an invasive procedure and can only be performed by healthcare workers. In contrast, saliva can be collected from patients easily. Recent studies have demonstrated that respiratory virus test results of saliva are comparable to those of nasopharyngeal specimens. Since January 2019, we have started to use saliva for the detection of respiratory viruses at the Accident and Emergency Department (AED). Here, our objectives are i) to analyze the saliva testing results during the 2019 winter season, and ii) to compare the results from nasopharyngeal specimen testing performed at the AED during the 2017/2018 winter and the 2017 summer epidemic. Methods Saliva specimens were collected from patients at the AED of Queen Mary Hospital, a University-affiliated tertiary hospital in Hong Kong. Saliva was tested using Xpert® Xpress Flu/RSV assay. Saliva test results were retrieved from the Laboratory Information System. Results From January 3 to February 28, 2019, a total of 487 saliva specimens were collected. The median age was 52 years, with an interquartile range of 30 to 70 years. Influenza A virus, influenza B virus and respiratory syncytial virus (RSV) were detected in 46% (222/487), 0.2% (1/487) and 1.6% (8/487) of patients, respectively. One patient had co-infection with influenza A virus and RSV. The percentage of specimens positive for influenza viruses in 2019 winter was similar to those of 2017/2018 winter influenza season (51%; 79/154) and of 2017 summer influenza season (43%; 23/53). Conclusion The detection rate of influenza viruses in saliva during 2019 winter is similar to that in previous influenza seasons when nasopharyngeal specimens were used. Saliva is a convenient specimen type that can be used for respiratory virus testing at AED.