Comparison of polyurethane foam to nylon flocked swabs for collection of secretions from the anterior nares in performance of a rapid influenza virus antigen test in a pediatric emergency department.
Author(s): Scansen KA, Bonsu BK, Stoner E, Mack K, Salamon D, Leber A, Marcon MJ
Publication: J Clin Microbiol, 2010, Vol. 48, Page 852-6
PubMed ID: 20053857 PubMed Review Paper? No
Purpose of Paper
This paper compared the sensitivity and specificity of influenza diagnosis using RT-PCR, direct immunofluorescence assay (DFA), and viral culture of nasopharyngeal specimen to diagnosis by immunoassay of polyurethane foam and flocked nylon nasal swabs specimens.
Conclusion of Paper
Using RT-PCR results from the nasopharyngeal swab specimens as the control, specificity and positive predictive value for influenza detection were comparable for both nasal specimen swab types but sensitivity, negative predictive value, and overall diagnostic accuracy were higher in the specimens collected with polyurethane foam swabs than those collected with flocked nylon swabs. When nasopharyngeal swab direct immunofluorescence assay and culture were used as the control, sensitivity for detection of influenza overall and of both influenza subtypes was higher in foam swabs than flocked nylon swabs but specificity, negative predictive value, and positive predictive value were similar between swab types. Overall diagnostic accuracy was lower for flocked swabs than foam swabs but did not reach statistical significance.
Studies
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Study Purpose
This study compared the sensitivity and specificity of influenza diagnosis using RT-PCR, direct immunofluorescence assay, and viral culture of nasopharyngeal specimen to diagnosis by immunoassay of polyurethane foam and flocked nylon nasal swabs specimens. Specimens were collected from 100 participants during two influenza seasons (January-March 2007 and January-February 2008, n=50 for each) with a fever of >100.4°F in the emergency department and/or in the last 48 h at home and presenting with two or more of the following symptoms: chills/sweats, cough, dyspnea, fatigue, headache, myalgia, nasal congestion, rhinorrhea, and/or sore throat. Nasal specimens were collected with a polyurethane foam-tipped swab in one naris and with a flocked, nylon fiber-tipped swab in the opposite naris. Swabs were rotated for several seconds, removed, and placed directly into separate dry transport tubes. Following the collection of the two nasal specimens, a single posterior nasopharyngeal swab was collected by inserting a Dacron polyester mini-tipped aluminum shaft swab into one naris past the turbinates until resistance was met at the level of the posterior nasopharynx, rotating the swab for several seconds, and then removal with further rotation. The swab tip was cut off and immediately placed in 2 mL viral transport medium. All specimens were immediately transported to the clinical virology laboratory within 30 min of collection. Nasal swabs were tested with a lateral-flow immunoassay (Quidel QuickVue Influenza A+B test). Nasopharyngeal swab specimens were analyzed for influenza by a direct immunofluorescence assay (DFA) using 1 mL of transport medium. Viral cultures were obtained from nasopharyngeal swab specimens by inoculating 0.2 mL of transport medium into two R-Mix vials, and incubation at 36°C for 42 h. One vial was stained with the SimulFluor respiratory screening reagent and, if positive, the second vial was stained with SimulFluor Flu A/B direct FA reagent to differentiate between virus types. RNA was extracted from 0.2 mL of transport medium from the nasopharyngeal swab specimen using an easyMag and influenza A and B virus RNAs were detected using an in-house RT-PCR method.
Summary of Findings:
Using RT-PCR results from the nasopharyngeal swab specimens as the control, sensitivity for detection of influenza was higher in the nasal specimens collected with polyurethane foam swabs than those collected with flocked nylon swabs for influenza A (81% versus 59%), influenza B (53% versus 42%), and overall (71% versus 54%) but specificity was 98% for both swab types. Negative predictive values for RT-PCR results from the nasopharyngeal swab specimens were higher for foam swabs than flocked swabs (73% versus 62%) but positive predictive values were similar between the swab type (98% versus 97%). Overall diagnostic accuracy for RT-PCR results from the nasopharyngeal swab specimens was 0.55 times lower with the flocked swab than with the foam swab (P=0.01). Similarly, when DFA and culture were used as the control, sensitivity for detection of influenza was higher in foam swabs than flocked nylon swabs for influenza A (85% versus 65%), influenza B (60% versus 53%), and overall (78% versus 61%). Specificity, negative predictive value, and positive predictive value for DFA and culture diagnosis from nasopharyngeal swabs were similar for foam swabs versus flocked swabs (93% versus 98%, 81% versus 72%, and 93% versus 97%, respectively). Overall diagnostic accuracy for DFA and culture diagnosis from nasopharyngeal swabs was lower for flocked swabs than foam swabs but did not reach statistical significance (P=0.13).
Biospecimens
Preservative Types
- None (Fresh)
Diagnoses:
- Pneumonia/Respiratory Infection
Platform:
Analyte Technology Platform RNA RT-PCR Protein Immunoassay Protein Immunofluorescence assay Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Biospecimen Acquisition Method of cell acquisition Polyurethane foam-tipped swab
Flocked nylon fiber-tipped swab
RT-PCR Specific Targeted nucleic acid Influenza A
Influenza B
Biospecimen Acquisition Biospecimen location Nasal Cavity
Nasopharynx