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One-Step Influenza A Test
One Step Influenza A Test is a rapid qualitative assay that detects influenza type A (including the subtype H1N1) nucleoprotein antigen extracted from the nasal swab specimen. The device is used to aid in the diagnosis of influenza type A infection.
For in vitro diagnostic use only. For professional use only.
Influenza (commonly known as ‘flu’) is a highly contagious, acute viral infection of the respiratory tract. It is a communicable disease that is easily transmitted through the coughing and sneezing of aerosolized droplets containing live virus. Influenza outbreaks occur each year during the autumn and winter months. There are three types of influenza viruses: A, B, and C. Only influenza A viruses are further classified by subtype on the basis of the two main surface glycoproteins hemagglutinin (HA) and neuraminidase (NA). Influenza A subtypes and B viruses are further classified by strains.
Humans can be infected with influenza types A, B, and C viruses. Subtypes of influenza A that are currently circulating among people worldwide include H1N1, H1N2, and H3N2 viruses. Influenza B viruses can cause morbidity and mortality among humans, but in general are associated with less severe epidemics than influenza A viruses. Although influenza type B viruses can cause human epidemics, they have not caused pandemics. Influenza type C viruses cause mild illness in humans and do not cause epidemics or pandemics.
One Step Influenza A Test is a rapid immunochromatographic test for the visual detection of influenza type A antigen (nucleoprotein) extracted from the nasal swab specimen. The test adopts double antibody sandwich method.
When the extracted specimen is added into the test device, the specimen is absorbed into the device by capillary action, mixes with antibody-dye conjugate, and flows across the membrane pre-coated with influenza type A monoclonal antibody.
When the influenza type A antigen levels are at or above the target cutoff (the detection limit of the test), type A antigen in the specimen binds to the specific antibody-dye conjugate and are captured by influenza type A monoclonal antibody immobilized in the relative site of test region “T” of the device. This produces a colored test band in the test region. When the influenza type A antigen levels are zero or below the target cut off, there is not a visible colored band in the test region of the device. This indicates a negative result for influenza type A.
To serve as a procedure control, a colored line will appear at the control region (C), if the test has been performed properly.
1.20 Individual sealed pouches, each containing
2. 20 Extraction tubes.
3.20 Nasal swabs.
4. Two dropper bottles of extraction buffer (each 5mL): 0.1M phosphate buffer saline (PBS).
5. Leaflet with instructions for use.
Material Required But Not Provided
STORAGE AND STABILITY
SPECIMEN COLLECTION AND PREPARATION
1.Take out the nasal swab provided. Tilt the head of the patient backwards to the angle of 70° and gently insert the nasal swab into the nostril which shows the most secretion.
2.Very gently rotate and push the swab until resistance is met at level of the turbinate. Gently rotate the swab against the nasal wall for a few times.
3.Patient samples perform best if tested immediately after collection.
If immediate testing is not possible, the swab should be placed in a dry, sterile plastic tube (not provided) and stored at 2ºC-4ºC for up to 8 hours.
Allow the test device, specimen, and extraction buffer to equilibrate to room temperature (10°C ~30°C) prior to testing.
1.Use an extraction tube (provided) for each specimen to be tested, and label each tube appropriately.
2.Hold the extraction buffer bottle upside down vertically, then add 8 drops (about 400μl) of extraction buffer to the extraction tube.
3.Place the specimen swab in the tube and swirl the swab for 10 times while pressing the swab head against the inside of the tube to release the specimen in the swab.
4.Remove the swab while squeezing the swab head against the inside of the collection tube as you remove it to expunge as much liquid as possible from the swab. Discard the swab. Cap the tube and mix contents by gently swirling. The extraction specimen must be tested immediately.
5.Remove the test device from its sealed foil pouch by tearing at the notch. Dispense 3~4 drops (80μl~100μl) of extraction specimen from the extraction tube into the sample well of the test device by inverting and squeezing the tube as shown.
6.Read the test results at 15~20 minutes. DO not read test results after 30 minutes.
INTERPRETATION OF RESULTS
Colored bands are visible in both the control region and the test region. It indicates a positive result for influenza type A antigen.
A colored band is visible only in the control region. No color band appears in the test region. It indicates that the concentration of the influenza type A antigen is zero or below the detection limit of the test.
No visible band at all, or there is a visible band only in the test region but not in the control region. Repeat with a new test kit.
Note: There is no meaning attributed to line color intensity or width.
A procedural control is included in the test. A colored line appearing in the control region (C) is considered an internal procedural control. It confirms sufficient specimen volume, adequate membrane wicking and correct procedural technique.
Good laboratory practice recommends the use of the control materials. Users should follow the appropriate federal state, and local guidelines concerning the frequency of assaying external quality control materials.
LIMITATIONS OF PROCEDURE
1.This test has been developed for testing nasal swab specimen only.
2.As it is with any diagnostic procedure, a confirmed diagnosis should only be made after all clinical and laboratory findings have been evaluated.
3.A negative test result may occur if the level of antigen in a sample is below the detection limit of the test, or from improper sample collection.
4.Negative test results are not intended to rule-out other non-influenza viral infections.
5.Positive test results do not rule out co-infections with other pathogens and does not identify specific influenza A virus subtypes.
The lowest detectable limit
For influenza type A : 5.1×105TCID50/ml
A comparison study of One Step Influenza A Test and another commercial influenza test (Colloidal gold method) was carried out in several medical institutions. Nasal swab samples were collected from adult and child patients exhibiting influenza-like symptoms. One swab was used to perform the One Step Influenza A Test and one swab was used for another commercial influenza test analysis.
Compare the sensitivity and specificity between the two tests. The results are summarized in Table 1.
Table 1: Comparison results
|One Step Influenza A Test||The reference test||Total|
|Influenza A positive||Influenza A negative|
|Influenza A positive||284||37||321|
|Influenza A negative||27||745||772|
(1) Sensitivity of One Step Influenza A Test is: 284/311×100％＝91.3％
(2) Specificity of One Step Influenza A Test is: 745／782×100％＝95.7％
One Step Influenza A Test was tested with the following influenza A viral strains listed in Table 2. All showed positive results. Although the specific influenza A strains causing infection in humans can vary year to year, all contain the conserved nucleoproteins targeted by the One Step Influenza A Test.
Table 2: Influenza A viral trains
|Influenza type A|
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