Comparison of nasopharyngeal flocked swabs and aspirates for rapid diagnosis of respiratory viruses in children.
BACKGROUND
The quality of clinical specimens is a crucial determinant for virological diagnosis.


OBJECTIVE
We compared the viral diagnostic yield for influenza A and respiratory syncytial virus (RSV) from the recently developed nasopharyngeal flocked swabs (NPFS) with nasopharyngeal aspirates (NPA) collected in parallel from 196 hospitalized children with acute respiratory infection during the peak period of influenza A and RSV activity in Hong Kong. Specimens were tested by RT-PCR for influenza A and RSV and viral load determined. They were also tested by direct immunofluorescence (DIF) for influenza A and B, RSV, parainfluenza types 1-3 and adenovirus.


RESULTS
Both NPA and NPFS had excellent sensitivity (100%) for detecting influenza A by RT-PCR but NPA was slightly more sensitive than NPFS for detecting RSV by both RT-PCR (100% vs. 92.3%) and DIF (87.2% vs. 84.6%) and for detecting influenza A by DIF (90.2% vs. 82.9%). Viral load for influenza A in NPA and NPFS was not significantly different but that for RSV was higher in NPA.


CONCLUSIONS
NPA remains the optimal specimen for diagnosis of respiratory infections by RT-PCR and DIF. However, collection of NPFS is easier to perform in an out-patient setting, was more acceptable to parents and less likely to generate aerosols than NPA engendering potentially less infection control hazard.
Chan
K H
KH
Department of Microbiology, The University of Hong Kong and Queen Mary Hospital, Hong Kong SAR, China.
Peiris
J S M
JS
Lim
W
W
Nicholls
J M
JM
Chiu
S S
SS
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D019085:Fluorescent Antibody Technique, Direct / Q000379:methods; D006723:Hong Kong; D006801:Humans; D007223:Infant; D009980:Influenza A virus / Q000302:isolation & purification; D009305:Nasopharynx / Q000821:virology*; D010222:Parainfluenza Virus 1, Human / Q000302:isolation & purification; D010223:Parainfluenza Virus 2, Human / Q000302:isolation & purification; D010224:Parainfluenza Virus 3, Human / Q000302:isolation & purification; D012136:Respiratory Syncytial Viruses / Q000302:isolation & purification; D012141:Respiratory Tract Infections / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods*; D014777:Virus Diseases / Q000821:virology*; D014780:Viruses / Q000235:genetics / Q000302:isolation & purification*