Flocked Swabs and UTMRT are Preanalytical Tools Suitable for Rapid Antigen Kits Direct Immunofluorescence Culture and PCR Diagnostics Assay for Viral Infections
Objective: Detection of antigens, nucleic acids, and isolation of microbes depend on pre-analytical devices used for specimen’s collection. Diagnostic sensitivity varies with the number of cells and free organisms released in the transport system. It was reported that Flocked Swabs (FS) and UTM-RT (Copan, Brescia Italy) enhances analytical sensitivity of antigen detection, culture and nucleic acid amplification assays. To compare the Copan FS and UTM-RT to the Remel Dacron swabs (DS) and M4-RT for virus culture, epithelial cells recovery for direct im munofluorescence assay (DFA), antigens and nucleic acids stability for rapid kits and amplification assays from nasopharyngeal swabs (NPS) for the diagnose of respiratory viruses.
Methods: 5002 consecutive NPS, collected with FS and UTM-RT, submitted to the Virology Laboratory from Nov.1, 2004 to Apr. 30, 2006, were compared to 4288 NPS collected with DS and M4-RT from Nov.1, 2002 to Apr. 30 2004. Of the NPS collected with FS and UTM-RT, 261 were analyzed for Flu A/B and 375 for hMPV by PCR, 291 were tested with 4 rapid antigen kits for RSV, flu A and B. All NPS were tested by DFA, cells pellets were spotted on glass slides, fixed and stained with the para 1, 2, and 3, flu A, and B, RSV, adenovirus and hMPV FITC antibodies. NPS were inoculated into R-Mix shell vial cultures. After 48 hrs, cells were fixed, and stained with the Pool and hMPV reagents. Pool positives were typed. For PCR, nucleic acids were extracted with the miniMAG system. 5 ul purified nucleic acid was test with the RealArt kit for Influenza A/B or with an hMPV specific RT-PCR.
Results: 1318/4288 were positive in the NPS collected with DS and M4-RT: DFA/culture had 538 flu A, 635 RSV, 10 para 1-3, 35 adenovirus; 2099/5002 were positive in the NPS collected with FS and UTM-RT: DFA/culture had 663 flu A, 277 flu B, 879 RSV, 171 para 1-3, 109 adenovirus; 101 positive out of 868 tested for hMPV. Antigen tests had 121 RSV, 33 flu A, 37 flu B and 100 negatives. The PCR detected 102/261 Flu, 66/375 hMPV. NPS collected with FS and UTM-RT detected 2009/5002 (42%) positive compared to1318/2288 (31%) positive detected in NPS collected with DS and M4-RT.
Conclusions: NPS collected with flocked swabs in UTM-RT detected a higher number positive than NPS collected with DS and M4-RT. The Copan flocked swabs and UTM-RT collection and transport system is a universal system compatible with rapid antigen kit, DFA, culture and PCR and supports the detection and growth of hMPV