Comparison of Nasal and Nasopharyngeal Swabs for Influenza Detection in Adults

1Epidemiology Research Center, Marshfield Clinic Research Foundation, Marshfield WI, USA.
Clinical Medicine & Research 06/2012; 10(4). DOI: 10.3121/cmr.2012.1084
Source: PubMed


Examine differences in the detection of influenza by specimen and test type using paired nasal and nasopharyngeal swabs.DesignProspective studySettingEnrollment took place between January and March of 2007 in a central Wisconsin population.ParticipantsAdult patients were screened and enrolled by trained research coordinators following medical encounters for acute respiratory illnesses of <10 days duration.Methods
Paired nasal and NP swabs were collected from consenting patients and tested by both real time reverse transcriptase polymerase chain reaction (rRT-PCR) and viral culture. A composite measure of positivity was used as the gold standard; cases included any positive result by rRT-PCR or viral culture from either specimen type.ResultsPaired samples were collected from 240 adults; 33 (14%) individuals tested positive for influenza by rRT-PCR. Using rRT-PCR, the sensitivity of the nasal swab was 89% (95% CI 78 - 99%) and the sensitivity of the nasopharyngeal swab was 94% (95% CI 87 - 100%), compared to a composite gold standard.Conclusion
Test sensitivity did not vary significantly by swab type when using a highly sensitive molecular diagnostic test, but power was limited to detect modest differences.

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    • "The type of sample can affect the diagnostic technique performance and a variety of different respiratory sampling methods (nasal, oro or nasopharyngeal, wash, swab, aspirate) have been applied for respiratory viruses detection with discrepant results [Ieven et al., 2007; Lieberman et al., 2009; Loeffelholz and Chonmaitree, 2010; Kim et al., 2011; Irving et al., 2012; Huijskens et al., 2014; Jeong et al., 2014]. There are few comparative studies of diagnostic methods done for all the common respiratory viruses [Lieberman et al., 2009] and the even fewer done in adults [Jeong et al., 2014]. "
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    • "Using nasal swabs can therefore facilitate increased participation in active surveillance studies to detect novel influenza viruses. When PCR is used for viral detection, nasal swabs are comparable in sensitivity to nasopharyngeal swabs (Irving et al., 2012; Sung et al., 2008). Previous work has examined the impact of storage temperature and time on viral recovery from nasal swabs (Fereidouni et al., 2012). "
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