Transcript QUICKVUEFLEX STREP A TEST

QUICKVUEFLEX
STREP A TEST
INTENDED USE

The QuickVue Flex Strep A Test allows for
the rapid detection of group A streptococcal
antigen directly from the patient throat swab
specimens. The test is intended for use as
an aid in the diagnosis of group A
streptococcal infection.
BACKGROUND

Group A betahemolytic
streptococci
(Streptococcus
pyogenes) is one of
the most commonly
encountered
pathogens in
humans.
BACKGROUND (cont.)

Group A Streptococcus inhabits the skin and upper
respiratory tract of humans but is rarely
considered as normal flora. It is transmitted
person to person by direct contact with mucosa,
secretions or by contamination droplets produced
by coughs or sneezes. The presence of Group A
Streptococcus is almost always considered
clinically significant.
BACKGROUND (cont.)

When present, Group A Streptococcus can
cause a variety of illnesses. It is the most
common cause of skin infections such as
impetigo and erysipelas. It can cause illness
such as tonsillitis, pharyngitis, and scarlet
fever which can lead to more serious
complications including rheumatic fever
and acute glomerulonephritis.
BACKGROUND (cont.)

Group A Streptococcus has also been called
“ flesh eating bacteria” because of it’s
ability to progress into deeper tissue and
organs which can cause systemic and life
threatening infections.
BACKGROUND (cont.)

Early diagnosis and treatment of Group A
Streptococcus infections is therefore very
important and helps to prevent further
complications of many of the previously
mentioned illnesses. The QUICKVUE FLEX
Strep A Test is a rapid screening test used for the
detection consumes little time when compared
with the 24-48 hours waiting period of more
conventional methods that require microscopic
examination, culture, and isolation of the bacteria.
PRINCIPLES OF THE TEST

THE QUICKVUE FLEX Strep A Test is a lateralflow immunoassay. The test, containing a highly
specific and sensitive antibody reactive to the
Strep A antigens, is specific to Group A. To
perform the test, a throat swab specimen is
collected. The extraction reagents are mixed in a
tube, resulting in a green color change, and the
swab is added in order for the antigenic
component of the bacteria to be extracted.
PRINCIPLES OF THE TEST
(cont.)

Extraction occurs within one minute, after which the
extracted sample is added to the Sample Well of the Test
Cassette. The extracted sample migrates by capillary
action through a pad consisting of a pink label containing
rabbit polyclonal anti-strep A antibody and a blue control
label. If the extracted solution contains strep A antigen, the
antigen will bind to the antibody coupled to the pink test
label which, in turn, will bind a second rabbit polyclonal
anti strep A antibody spotted on the membrane, resulting in
the formation of a pink-to-purple Test line.
PRINCIPLES OF THE TEST
(cont.)

A blue Control Line will also appear next to the
letter “C” on the Test Cassette indicating that the
reagents were mixed and added properly, proper
volume of fluid entered the Test Cassette and
capillary flow occurred. A blue Control Line
should always appear in a properly functioning
Test Cassette. If strep A is not present or present
at very low levels, only a blue Control Line will
be visible.
REAGENTS & MATERIALS
Come in individually packaged Test Cassettes
 Rabbit polyclonal antibody to strep A (Test Line)
and a control rabbit polyclonal antibody capable
of binding the blue control label (Control Line)
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EXTRACTION REAGENT A
( 4M Sodium Nitrite)
EXTRACTION REAGENT B
(.2M Acetic Acid)
Sterile rayon-tipped swabs on solid plastic shafts
Tubes and tips
Positive Control Swabs
Negative Control Swabs
Package Insert
Procedure Card
TEST PROCEDURE

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
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Streak a BAP prior to beginning the
extraction procedure.
For each specimen and control:
Add 4 drops of Extraction Reagent A
into a clean Tube
Add 4 drops of Extraction Reagent B.
The solution should turn green when
Extraction Reagent B is added.
PROCEDURE, cont.
Immediately add the
throat swab
specimen to the Tube
containing the green
extraction solution.
 Rotate the swab
three times.
 Wait one minute.
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PROCEDURE, cont.
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Express all liquid from
the swab head in the Tube
by rolling the swab
against the inside of the
Tube and squeezing
firmly as it is withdrawn.
Discard the swab.
PROCEDURE, cont.
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Put a clean tip on
the Tube.
PROCEDURE, cont.
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Remove Test
Cassette from foil
pouch and place on
a clean, dry surface.
Add 2 drops from
the Tube to the
round Sample Well
on the Test Cassette.
PROCEDURE, cont.
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Read results at 5 minutes. Some positive
results may be seen earlier, but negative
results must be held the entire 5 minutes
and no longer.
INTERPRETATION OF
RESULTS

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Positive results:
appearance of any pink
to purple Test Line next
to the “T” in the result
window.
Positive QuickVue Flex
Strep A Test result
indicates that the
specimen contains
group A streptococcal
antigen.
INTERPRETATION OF
RESULTS (cont.)

Negative Result:
Only the blue Control
Line appears next to
the letter “C” in the
Result Window.
INTERPRETATION OF
RESULTS (cont.)

A negative QuickVue Flex Strep A Test
result indicates that the specimen is a
presumptive negative for the presence of
group A streptococcal antigen, pending the
result of the BAP streaked prior to the
beginning of the extraction procedure.
INVALID RESULT

The test result is
invalid if any shade
of blue Control Line
next to the letter “C”
is not visible at 5
minutes. If this
occurs, retest using a
new specimen and a
new Test Cassette.
PROCEDURE LIMITATIONS

This procedure used for qualitative detection of
group A streptococcal antigen from throat swab
specimen only. Failure to follow the test
procedure and interpretation of test results may
adversely affect performance and /or produce
invalid results.
PROCEDURE LIMITATIONS

QuickVue Flex Strep A Test will not
differentiate asymptomatic carriers of group
A Streptococcus from those exhibiting
streptococcal infection. In rare cases, test
specimens heavily colonized with
Staphylococcus aureus can yield false
positive results.
PROCEDURE LIMITATIONS

A negative test result might occur if the level of
extracted antigen in a sample is below the
sensitivity of the test. Additional follow-up testing
using the culture method is recommended if the
QuickVue test result is negative.
CONCLUSION
QUICKVUE FLEX TEST:
 Is a rapid, specific and sensitive test for detection of
Group A Streptococcus ( Streptococcus pyogenes)
antigen directly from patient throat swab specimen.
 It allows the physician to do quick diagnoses based on
the results.
 It avoids the 24-48 hours incubation time for blood
culture plate tests.
 This test is much more expensive than blood agar.