Table 2. Influenza Testing Methods (all A-II)
Test Description
Methods
RT-PCR
Time to
Results
Conventional gel-based real≥2 h
time RT-PCR
Multiplex PCR
Immunoflourescencea DFA staining
2–4 h
• Detects and distinguishes
between influenza A and B
• Detects and distinguishes
between influenza (A and B)
and other respiratory viruses
IFA staining
• Detects and distinguishes
between influenza A and B
• Detects and distinguishes
between influenza (A and B)
and other respiratory viruses
Rapid influenza
Antigen detection: enzyme
10–20
immunoassay
diagnostic testsb
min
• Detects influenza A only
• Detects, but does not
distinguish between,
influenza A and B
• Detects and distinguishes
between influenza A and B
Neuraminidase detection assay 20–30
• Detects, but does not
min
distinguish between,
influenza A and B
Viral culture
Shell vial culture
48–72 h
Isolation in cell culture
3–10 d
Serologyc
Hemagglutinin inhibition
ELISA
Complement-fixation
Neutralization
Comment
High sensitivity, very
high specificity;
highly recommended
Moderately
high sensitivity,
high specificity;
recommended
Low to moderate
sensitivity, high
specificity;
limitations should
be recognized to
interpret results
Moderately high
sensitivity, highest
specificity; important
for confirming
screening test results
and for public health
surveillance, but not
useful for timely
clinical management
Available only in
reference laboratories,
not useful for timely
clinical management;
recommended only
for retrospective
diagnosis, surveillance,
or research purposes
DFA, direct fluorescent antibody; ELISA, enzyme-linked immunosorbent assay; IFA, indirect
fluorescent antibody; RT-PCR, reverse transcriptase polymerase chain reaction.
a
Requires fluorescence microscope.
b
Includes moderately complex and Clinical Laboratory Improvement Amendments (CLIA)-waived
tests.
c
Usually requires paired acute and convalescent sera.
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