Improving the Quality of Nasal Specimen Collection for Influenza A and B Screening

PROBLEM: Rapid diagnosis of seasonal influenza leads to optimized clinical care and reduces the spread of infection. The collection of adequate cellular material can be facilitated by the presence of moisture in the nares. The specific aim of this project was to determine if the installation of sterile saline into the nares prior to specimen collection would improve the quality of the specimen.

This quasi-experimental single group design tested an initial "dry swab" specimen against a second swab after instillation of sterile saline solution using a nasal atomizer, a "wet swab."

A total of 80 paired specimens were collected and analyzed between December 7, 2015, and April 21, 2016, with an 11.25% infection rate in those tested. Of 9 positive tests, 6 subjects tested positive for influenza A or B for both the dry swab and the wet swab. Three subjects tested positive for influenza A or B for only the wet swab, and these subjects had experienced their symptoms longer than did subjects who tested positive for both methods (mean symptom onset of 72 hours vs 66 hours). We found an important inconsistency between manufacturers' recommendations and typical hospital practice.

The results appear somewhat equivocal. Because viral shedding declines after the first 48 to 72 hours in adults, the wet swab method may be clinically superior for detecting influenza in adults presenting later in the course of their illness. Hospital policy was revised for consistency in using the gel medium before sampling in accordance with manufacturer recommendations.