Performance of laboratory diagnostics for the detection of influenza A(H1N1)v virus as correlated with the time after symptom onset and viral load.
BACKGROUND
To diagnose influenza A(H1N1)v virus infection, accurate and rapid detection are important. However, there is scanty data on the performance of various laboratory diagnostics.


OBJECTIVE
To compare the performance of rapid antigen test (RAT), viral culture and RT-PCR for the detection of influenza A(H1N1)v virus and to correlate their performance with the time after symptom onset and viral load.


METHODS
From May 1, 2009 to June 25, 2009, respiratory samples were collected from 5740 individuals suspected of having influenza A(H1N1)v infection. The performance of viral culture and RT-PCR were investigated and correlated with the time after symptom onset. The sensitivity of RAT ESPLINE influenza A & B-N (Fujirebio Inc, Tokyo) was evaluated using a subset of 60 samples from patients diagnosed as having influenza A(H1N1)v infection.


RESULTS
Using respiratory samples from 587 patients diagnosed with influenza A(H1N1)v infection, comparison of laboratory diagnostics showed viral culture and RT-PCR gave comparable results with overall sensitivity of 93.9% and 98.1%, respectively. For RAT, when testing a subset of 60 samples collected < or =3 days following symptom onset, the sensitivity was 62%.


CONCLUSIONS
Although viral shedding is prolonged and of higher titre in influenza A(H1N1)v infection, RAT showed a low sensitivity of 62% among patients presenting < or =3 days after symptom onset. Viral culture showed comparable performance with RT-PCR and with sensitivity better than that documented for seasonal influenza.
Cheng
Peter K C
PK
Centre for Health Protection, Department of Health, Hong Kong, People's Republic of China.
Wong
Kitty K Y
KK
Mak
Gannon C
GC
Wong
Ann H
AH
Ng
Anita Y Y
AY
Chow
Salina Y K
SY
Lam
Ricky K H
RK
Lau
C S
CS
Ng
K C
KC
Lim
Wilina
W
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D019411:Clinical Laboratory Techniques / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000175:diagnosis* / Q000473:pathology / Q000821:virology*; D008297:Male; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D013997:Time Factors; D019562:Viral Load; D014776:Virus Cultivation / Q000379:methods; D055815:Young Adult