Comparison of nasal and nasopharyngeal swabs for influenza detection in adults.
OBJECTIVE
Examine differences in the detection of influenza by specimen and test type using paired nasal and nasopharyngeal swabs.


METHODS
Prospective study


METHODS
Enrollment took place between January and March 2007 in a central Wisconsin population.


METHODS
Adult patients were screened and enrolled by trained research coordinators following medical encounters for acute respiratory illnesses of <10 days duration.


METHODS
Paired nasal and nasopharyngeal swabs were collected from consenting patients and tested by both real-time reverse transcriptase polymerase chain reaction (rRT-PCR) and viral culture. A composite measure of positivity was used as the gold standard; cases included any positive result by rRT-PCR or viral culture from either specimen type.


RESULTS
Paired samples were collected from 240 adults; 33 (14%) individuals tested positive for influenza by rRT-PCR. Using rRT-PCR, the sensitivity of the nasal swab was 89% (95% CI, 78%-99%) and the sensitivity of the nasopharyngeal swab was 94% (95% CI, 87%-100%), compared to a composite gold standard.


CONCLUSIONS
Test sensitivity did not vary significantly by swab type when using a highly sensitive molecular diagnostic test, but power was limited to detect modest differences.
Epidemiology Research Center, Marshfield Clinic Research Foundation, Marshfield, WI, USA. stephanie_irving@abtassoc.com
Stephanie A
SA
Irving
Mary F
MF
Vandermause
David K
DK
Shay
Edward A
EA
Belongia
D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D009980:Influenza A virus / Q000302:isolation & purification*; D009981:Influenza B virus / Q000302:isolation & purification*; D007251:Influenza, Human / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D009305:Nasopharynx / Q000821:virology*; D009666:Nose / Q000821:virology*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods*; D014773:Virology / Q000379:methods