ACCU-TELL STREP A TEST (CE)

Declaration: As with all diagnostic tests, a definitive clinical diagnosis should not be based on the result of a single test, but should only be made by the physician after all clinical and laboratory findings have been evaluated.

CATALOG

INTENDED USE

SUMMARY AND EXPLANATION
TEST PRINCIPLE
STORAGE
WARNING AND PRECAUTIONS
SPECIMEN COLLECTION AND STORAGE
ASSAY PROCEDURE
TEST PROCEDURE
INTERPRETATION OF TEST RESULTS 
QUALITY CONTROL
LIMITATIONS
EXPECTED RESULTS 
PERFORMANCE CHARACTERISTICS
REFERENCES

CATALOG

Catalog No.                    Product Name                      Note

ABT-IDT-B15                  Strep A Cassette                  CE

INTENDED USE
Accu-Tell ^® Rapid Strep A Test is a lateral flow, one-step immunoassay for the rapid, qualitative detection of Group A Streptococcal antigen directly from throat swabs.

SUMMARY AND EXPLANATION
Beta-hemolytic Group A Streptococcus is a major cause of upper respiratory infections such as tonsillitis, pharyngitis and scarlet fever. Early diagnosis and treatment of Group A Streptococcal pharyngitis has been shown to reduce the severity of symptoms and further complications, such as rheumatic fever and glomerulonephritis. Conventional methods used for the detection of the disease depend on the isolation and subsequent identification of the organism. These methods often require 24-48 hours to complete. Recent development of immunological techniques which can detect Group A Streptococcal antigen directly from throat swabs allow physicians to diagnose and administer therapy immediately.

TEST PRINCIPLE
Accu-Tell ^® Rapid Strep A Test utilizes two site sandwich immunoassay technology for the detection of Group A Streptococcal antigen. The test device consists of plastic housing containing a membrane strip which has been precoated with rabbit anti-Strep A antibody on the test band region and goat anti-rabbit antibody on the control band region. A colored rabbit anti-Strep A polyclonal antibody-colloid gold conjugate pad is placed at the end of the membrane. During testing, the Strep A antigen is extracted from the throat swab using Extraction Reagents 1&2. The extracted solution is then added to the sample well. The Strep A antigen reacts with colored antibody-colloidal gold conjugate to form Strep A antigen-antibody complexes. The mixture then moves chromatographically across the membrane to the immobilized rabbit anti-Strep A antibody at the test band region. If Strep A antigen is present in the specimen, a pink colored sandwich of solid phase/Strep A antigen/gold conjugate is formed on the test band region. Absence of the pink colored band at the test band region indicates a negative result. Regardless of the presence of Strep A antigen, as the extracted mixture continues to move laterally across the membrane to the immobilized goat anti-rabbit antibody test band region, a pink colored band at the control region will always appear. The presence of this colored band serves as: 1) verification that sufficient volume has been added, 2) verification that proper flow is abtained, and 3) reagent control.

STORAGE
All reagents included in the Strep A Test can be stored at room temperature or refrigerated (2- 30°C).

WARNING AND PRECAUTIONS
1.  For in vitro diagnostic use only !
2.  Do not mix reagents from different lots.
3.  Do not use after stated expiration date.
4.  Do not mix reagent bottle caps.
5.  Extraction Reagents 1, 2 and 3 are slightly caustic. Avoid contact with eyes or mucous membranes. In the event of accidental contact, wash thoroughly with water.
6.  Positive and Negative Controls contain sodium azide which may react with lead or copper plumbing to form potentially explosive metal azides. When disposing of these solutions, always flush with copious amounts of water to prevent azide buildup.
7.  Standard guidelines for handling infectious agents and chemical reagents should be observed throughout all procedures. All contaminated waste such as swabs, Strep A Test devices and extracts should be properly disposed.

SPECIMEN COLLECTION AND STORAGE
Collect throat swab specimens by standard clinical methods such as those described by Facklam (1) and Ross (5). Use only Dacron or Rayon tipped sterile swabs with plastic shafts such as those provided. Do not use calcium alginate, cotton tipped, or wooden shafted swabs.
It is recommended that swabs specimens be processed as soon as possible after collection. If swabs are not processed immediately, they should be placed into a sterile, dry, tightly capped tube or bottle and refrigerated. If a liquid transport methods is employed, use Modified Stuart’s Transport Media as outlined in the manufacture’s instructions. Do not use transport media formulas including charcoal or agar. Swabs can be stored at room temperature ( 15-30℃) up to 4 hours, or refrigerated (2-8℃) up to 24 hours.
If a bacteria culture is desired, lightly streak the swab on a 5% sheep blood agar plate before using it in the Accu-Tell ^®Strep A Test. Extraction reagents kill the bacteria on swabs and make them impossible to culture. Alternatively, a subsequent second swab sample may be taken for culture procedure.

ASSAY PROCEDURE
Procedural Notes
1.  If specimen swabs or any Strep A Test reagents have been refrigerated, allow them to equilibrate to room temperature before testing.
2.  To avoid cross contamination, do not allow the tips of the reagent bottles to come in contact with sample swabs and Extraction Tubes.
Extraction Procedure
1.  Place an Extraction Tube in the designated areas of the Workstation. Add 4 drops of Extraction Reagent 1 to the Extraction Tubes.
2.  Add 4 drops of Extraction Reagent 2 to the tube. Immediately place the throat swab specimen in the tube. Use a circular motion to roll the swab against the side of the Extraction Tube so that the liquid is expressed from the swab and reabsorbed. Let stand for a minimum of 1 minute at room temperature and maximum of 15 minutes.

TEST PROCEDURE
1.  Cap the Extraction Tube with the attached dropper. Add all the extracted solution to the Sample well of the test device.
2.  Read result in 5 minutes. Depending on the number of the organisms on the swab, positive result may be visible as soon as 1 minute. However, to confirm a negative result the complete reaction time of 5 minutes is required. Do not read result after 10 minutes.

INTERPRETATION OF TEST RESULTS
Negative: A pink-colored band appears in the control (C) region. No pink colored band is visible in the test (T) region. This indicates that no Strep A antigen has been detected.
Positive: In addition to a pink-colored band in the control (C) region, a pink-colored band will appear in the test (T) region. These bands may be any shade of pink. This indicates that the specimen contains Strep A antigen.
Invalid: No band appears in either the control or the test region. This indicates a possible error in performing the test. A new test should be performed.

QUALITY CONTROL
Good laboratory practice recommends the use of control materials to ensure proper kit performance. A positive control containing heat-killed Group A Streptococcus and a negative control containing heat-killed Group B Streptococcus are provided with each kit.
Positive control: Add 4 drops of Extraction Reagent 1 and 4 drops of Extraction Reagent 2 to an Extraction Tube. Thoroughly mix the Positive Control by shaking the bottle vigorously. Add 1 drop of Positive Control to the tube. Place a sterile swab into the tube and swirl.
Negative Control: Add 4 drops of Extraction Reagent 1 and 2 to an Extraction Tube. Thoroughly mix the Negative Control by shaking the bottle vigorously. Add 1 drop of Negative Control to the tube. Place a sterile swab into the tube and swirl.

LIMITATIONS
1.  The accuracy of the test depends on the quality of the swab sample. False negatives may result from improper sample collection or storage. A negative result may be obtained from patients at the onset of the disease due to low antigen concentration. Therefore, when a patient suspected of having Strep A pharyngitis has a negative Accu-Tell ^®Strep A test result, additional testing using the culture method is required.
2.  The test does not differentiate asymptomatic carriers of Group A Streptococcus from those with infection. If clinical signs and symptoms are not consistent with laboratory test results, a follow-up throat culture is recommended.
3.   In rare cases, test specimens heavily colonized with Staphylococcus aureus can yield false positive results. If clinical signs and symptoms are not consistent with clinical test results, a follow-up culture and grouping procedure should be performed.
4.   Respiratory infections, including pharyngitis, can be caused by Streptococci from serogroups other than Group A, as well as by other pathogens.
5. As in the case of any diagnostic procedure, the results obtained with this test should be used in conjunction with other information available to the physician.

EXPECTED RESULTS
It is believed that approximately 19% of all upper respiratory tract infections are caused by Group A Streptococci. Infection is most prevalent in winter and early spring, with most cases arising in patients living in highly populated areas.

PERFORMANCE CHARACTERISTICS
Sensitivity (Detectable Limits) Study
To determine the analytical sensitivity of the Accu-Tell ^® Strep A Test, Group A Streptococcus bacteria organisms were grown by standard culture techniques. The detection limit of the Strep A Test was determined to be 1.5×10⁵ organisms per test.
Specificity Study
To determine the specificity of the Accu-Tell ^® Strep A Test to Group A Streptococcal bacteria, the following Group A Streptococcal Strains at different levels of organisms pet test were examined. Positive results obtained at level of 1.5×10⁵ organisms/test for all strains indicate that Accu-Tell ^® Strep A Test is sensitive to Group A Streptococcal bacteria.
Group A Streptococcal Strains:

Cross-reactivity studies with organisms likely to be found in the respiratory trace were also performed using the Accu-Tell ^® Strep A Test. The following organisms were tested at 1×10⁸ organisms/test.

Accu-Tell ^®Strep A Test gave negative results in all cases.
Correlation Study
A correlation study between Accu-Tell ^® Strep A Test and the conventional culture tests has been determined in multi-center clinical evaluations. Throat swab specimens were taken from children and adults exhibiting symptoms of pharyngitis. The swabs were then used to inoculate blood agar plates prior to testing with the Accu-Tell ^® Strep A Test. Beta-hemolytic colonies from the blood agar plates were confirmed as Group A Streptococcus using serologic streptococcal grouping methods. Strep A was reported as present or not present. Semiquantitation was not performed during testing of clinical samples.
The results are summarized as follows:

Sensitivity
90.5% (95% Cl,84.2% to 96.8%)
Specificity
97.5% (95% Cl,93.7% to 99.3%)
physician Office Laboratory Studies
An evaluation of Accu-Tell ^® Strep A Test was conducted at three Physician Office Laboratory sites, using a panel of coded samples containing Negative Control, Low Positive and Medium Positive specimens. Each specimen level was tested in replicates of five, at each site, over a period of five days, One hundred percent(100%) agreement with the expected results was obtained.

REFERENCES
1.  Facklam, R. R. and Carey, R. B.: Streptococci and aerococci. Manual of Clinical Microbiology, 4th ed., Lennette, E. H., Balows, A., Hausler, W. J. and Shadomy, H. J. (eds), American Society for Microbiology, 1985, 154-175.
2.  Levinson, M. L. and Frank, P. F.: Differentiation of Group A from other Beta Hemolytic Streptococci with Bacitracin. J. Bacteriol., 69, 284-287 (1955).
3.  Edwards E. A., Phillips, I. A. and Suiter, W. C.: Diagnosis of Group A Streptococcal Infections Directly from Throat Secretions. J. Clin. Micro., 15, 481-483 (1982).
4.  Gupta, R., Talwar, G. P. and Gupta S. K.: Rapid Antibody Capture Assay for Detection of Group A Streptococci Using Monoclonal Antibody and Colloidal Gold-Monospecific Polyvalent Antibody Conjugate. J. Immunoassay, 13, 441-445 (1992).
5.  Ross, P. W.: Throat Swabs and Swabbling Technique. The Practitioner, 207, 791-796 (1971).
6.  Lauer, B. A., Rellar, L B. and Mirrett, S.: Effect of Atmosphere and Duration of Incubation on Primary Isolation of Group A Streptococci from Throat Cultures. J. Clin. Micro., 17, 338-340 (1983).

Related Study Report by European Society of Clinical Microbiology and Infectious Diseases.

The above information is just for reference. The actual technical specifications are subject to the insert provided with the product.