Validation of Dry Flocked Swabs after Storage for the Detection of Influenza A Using Real Time PCR

Background:
Detection of influenza is usually done on swabs transported in viral transport medium. Dry swabs are preserving and stabilizing nucleic acids for molecular diagnosis.
Objectives:
To validate Copan dry flocked swabs to stabilize influenza A viral RNA using real time PCR.
Methods:
Flocked throat swabs (TS) and nasopharyngeal swabs (NPS) were compared to Dacron TS and NPS swabs. An influenza ATCC strain was titrated in cell culture and by PCR. Dilutions above and at the limit of detection were used as contrived specimens and dispensed in one ml aliquots in sterile tubes. Each swab type was dipped to simulate a TS and NPS, then placed into a sterile dry tube and stored at room temperature (RT) or 4° C for 3 weeks. Clinical nasopharyngeal swabs (50), stored dry, were also tested. 300 microliters was used to extract viral RNA using the Qiagen RNeasy Mini Kit, and tested in the Arrow Diagnostics Fast set real time assay on the Rotor Genie.
Results:
The contrived specimens prepared with flocked TS and NPS were positive for influenza A RNA up to 3 weeks when stored at 4° C and RT. Instead the Dacron TS and NPA were positive up to 3 weeks at 4° C, but negative at RT after two weeks. Fifteen of the 50 patient flocked NPS transported dry were positive after 3 weeks at RT.
Conclusions:
The Copan flocked TS and NPS demonstrated the ability to stabilize influenza A viral RNA when stored dry at RT or 4° C up to 3 weeks.