influenza tests require a nasal swab to determine the type of influenza virus.
Occasionally a blood sample is required for antibody testing. A variety of tests
can determine the type of influenza virus in less than 30 minutes, though they
are not as accurate as tests that take longer to obtain results.
Rapid Influenza Diagnostic Test (RIDT)
RIDT is a
test that can quickly determine whether or not an infection is caused by the
flu virus. A number of rapid tests are available, and they all require a simple
nasal swab. The results are usually available on the same day. Rapid tests are
most accurate when administered within the first 48 hours after symptoms
appear. Some rapid tests can distinguish between flu virus types, but none of
them can identify subtypes. The tradeoff for the speed of these tests is that
they can miss up to 30 percent of flu infections.
Direct Fluorescent Antibody Stain
uses a nasal swab to determine the presence or absence of antibodies to the
influenza virus in nasal secretions. The test can tell the difference between
Type A and Type B virus, but it is unable to distinguish between virus subtypes
of type A viruses like H1N1 or H3N2.
Influenza Virus Culture Test
culture test is the most accurate test for influenza and can determine both
virus type and subtype. A nasal swab is taken, and a culture of the virus is
grown in a laboratory culture. Results can take three to 10 days, so a culture
test is most often used by physicians to determine the dominant strain of virus
circulating in a community or to find out whether unusual cases indicate a new
strain is present.
secondary infections like pneumonia or other complications are present, your
physician may order other tests or procedures, including chest X-rays, sputum
cultures, or blood tests.