Cardinal Health™ Strep A Dipstick Rapid Test

Intended Use

Cardinal Health™ Strep A Dipstick Rapid Test - Direct Group A Streptococcus Antigen Test Strip is a rapid immunochromatographic assay for the qualitative detection of group A streptococcal antigen directly from throat swab specimens. The test is intended for use in physician's offices, hospitals, and clinical laboratories as an aid in the clinical diagnosis of group A streptococcal infection.

Summary and Explanation

Group A streptococcus is a significant pathogen causing acute pharyngitis, tonsillitis, impetigo, and scarlet fever. Differentiating streptococcal infection from other agents (e.g., viral, mycoplasmal, or chlamydial) is crucial for initiating appropriate therapy. Traditional methods require 18-48 hours for culture results. Rapid diagnosis and timely treatment of group A streptococcal pharyngitis can reduce symptom severity and prevent complications like rheumatic fever and glomerulonephritis.

Principle

The Cardinal Health™ Strep A Dipstick Rapid Test is a rapid immunochromatographic assay for the qualitative detection of group A streptococcal antigen directly from throat swabs. The test involves chemical extraction of the antigen followed by solid-phase immunoassay technology. A throat swab specimen is collected, mixed with Reagent A and B for extraction, and then the test strip is inserted into the tube. If group A streptococci are present, they react with the conjugate dye and the antibody on the test line, forming a colored Test line. The sample then migrates to the control area, where an antibody to the strep A antibody is immobilized, forming a Control line. The presence of both lines indicates a positive result. The absence of a Test line indicates a negative result. The Control line ensures test integrity, proper sample amount, and correct wicking chemistry. An invalid test requires repeating with a new strip and swab.

Reagents and Materials Provided

• 2 canisters containing 25 Cardinal Health™ Strep A Dipstick Rapid Test strips each.
• Cardinal Health™ Strep A Dipstick Rapid Test strip: Contains a membrane coated with rabbit anti-group A streptococcus antibody for the test line and a second control antibody, and a conjugate pad impregnated with the rabbit anti-strep A antibody-dye complex.
• Extraction Reagent A (13 mL): 2.0 M sodium nitrite solution. (Warning: Avoid contact with eyes or skin.)
• Extraction Reagent B (13 mL): 0.2 M phosphoric acid solution. (Warning: Avoid contact with eyes or skin.)
• Positive Control (1 mL): Extracted (non-infective) group A streptococcus antigen (equivalent to approximately 1 X 10⁷ CFU/ml) in phosphate buffered saline containing 0.1% sodium azide.
• Negative Control (1 mL): Extracted (non-infective) group B streptococcus antigen in phosphate buffered saline containing 0.1% sodium azide.
• Extraction Tubes (50)
• Throat Swabs (50): Rayon swab with plastic shaft (use only the swabs supplied).
• Instructions for Use.
• Reaction tube rack.

Materials Required but Not Provided

• Timer
• Gloves

Warnings and Precautions

• For in vitro diagnostic use only.
• Do not interchange materials from different product lots.
• Do not use after the expiration date indicated.
• Use only with the supplied swabs.
• Do not interchange caps between reagents.
• Reagents A and B are slightly caustic; avoid contact with eyes, sensitive mucous membranes, cuts, abrasions. Flush with water if contact occurs.
• Do not smoke, eat, or drink in handling areas.
• Wear disposable gloves and wash hands thoroughly after handling.
• Handle all patient samples as potentially infectious. Observe precautions against microbiological hazards and follow proper disposal procedures.
• Keep test strips in the closed canister until use. Do not use if the seal is broken.
• Control solutions contain sodium azide; avoid contact with lead or copper plumbing to prevent explosive metal azides. Flush reagents with large volumes of water during disposal.

Storage and Stability

Store test strips at 2-30°C (35-86°F) in the canister, out of direct sunlight. Do not freeze. Kit contents are stable until the expiration date. Strips are stable for 60 days after opening the canister.

Specimen Collection and Preparation

Collect throat swab specimens using the sterile rayon swabs supplied. Swabs should be processed within 4 hours of collection or stored refrigerated (2-8°C) for up to 24 hours. For cultures, collect two swabs; use one for immediate testing and store the second in liquid medium (approx. 200 µL) for up to 24 hours refrigerated. Avoid touching the sides of the mouth during collection. Excess saliva or blood can interfere with results.

Procedure

1. Add 4 drops each of Reagent A (yellow) and Reagent B to the extraction tube. Mix by gentle shaking until the solution turns pink.
2. Immediately place the swab into the tube.
3. Rotate the swab vigorously in the extraction solution for thorough extraction.
4. Let stand for 1-2 minutes.
5. Squeeze out as much liquid as possible from the swab by pressing it against the side of the tube with two fingers.
6. Discard the swab.
7. Remove a test strip from the sealed canister.
8. Insert the test strip into the tube of extracted solution to begin migration.
9. Read the result in 5 minutes, but no later than 10 minutes after dipping the strip. A distinct color line must have formed in the reading window.

Interpretation of Results

Positive: Two reddish-purple lines (Control and Test) indicate the presence of group A streptococcal antigen. The Test line intensity may vary. The Control line intensity should not be compared to the Test line.

Negative: One colored line in the Control area and no distinct colored line in the Test area indicate no detectable group A streptococcal antigen. Presumptive negative results should be confirmed by culture, as recommended by the American Academy of Pediatrics.

Invalid: A distinct colored line in the Control area (C) must always appear. If no Control line forms within 5 minutes, the test is invalid and must be repeated with a new test strip and swab.

Quality Control

External Quality Control: Use provided positive and negative controls to ensure reagent and user performance. If controls do not perform as expected, review instructions and repeat the test or contact Cardinal Health. The built-in Control line indicates test strip integrity and fluid flow. It is recommended to test controls before using a new lot or shipment. Frequency of additional QC should follow laboratory procedures. The Negative control should yield a negative result (Control line only). The Positive control should produce a moderate positive result (two lines). Known live cultures of Streptococcus pyogenes (ATCC strain 19615) or group C streptococci (ATCC strain 12388) can also be used for QC. The provided controls do not monitor the extraction step. Do not report patient results if controls do not perform as expected. Use of controls from other kits has not been established.

Internal Procedural Control: A colored line in the Control line area (pinkish-purple) indicates the test was performed correctly. If the control line does not appear, the test is invalid. A clear background in the result area indicates a negative procedural control.

Limitations

• Results should be used as an adjunct to other clinical information.
• The test is for qualitative detection of Strep A antigen only.
• The test does not differentiate between a carrier and an infected individual.
• The test can detect non-viable as well as viable organisms.
• Test results should be compared with culture identification until laboratory equivalences are established. Follow-up culture testing is recommended for negative results if Strep A infection is suspected.
• Specimens heavily colonized with Staphylococcus aureus (> 10¹⁰ CFU/mL) may yield false positive results.
• Proper throat swabs are essential for good test quality.
• Pharyngitis can be caused by organisms other than group A Streptococcus. This test only indicates the possibility of Strep A infection. If clinical signs and symptoms are inconsistent with results, a follow-up throat culture is recommended.
• A negative result may occur due to poor sample collection or low antigen levels at the onset of disease. Repeat testing with a fresh sample is recommended if symptoms persist.
• Swabs transported in liquid media may result in reduced sensitivity due to dilution.

Expected Values

Group A streptococcus infection is seasonal, peaking in winter and early spring. Approximately 19% of upper respiratory tract infections are caused by group A streptococcus, with the highest incidence in school-aged children and military personnel. Both males and females are equally affected.

Performance Characteristics

Clinical Correlation: The test was compared to FDA-cleared device tests and conventional plate culture techniques using 505 clinical specimens from patients with pharyngitis symptoms. The results showed 98.7% specificity and 96.2% sensitivity when compared to confirmed culture results.

Analytical Sensitivity: The analytical sensitivity of the test is 1.5 x 10⁵ CFU/mL, determined by testing serial dilutions of known organisms (ATCC 14285 or ATCC 19615).

Cross-Reactivity: Organisms commonly found in the respiratory tract were tested at 1 x 10⁷ organisms/mL. All results were negative, confirming the specificity of the test. Spiking with a positive Strep A control confirmed expected test results.

Reproducibility Study: Reproducibility was examined at two POL sites and a clinical laboratory using 15 blind control samples (5 negative, 5 low positive, 5 medium positive). Results showed 100% agreement with expected results at each site.

Distribution of Random Error: Twenty blind samples with varying concentrations of group A streptococcal antigen were tested by two operators with complete agreement in results.

Symbols Glossary

Temperature Limitation: 36°F (2°C) to 86°F (30°C) ? Keep away from sunlight.

Non Sterile: Non-Sterile

Rx ONLY: Prescription Only

IVD: In vitro diagnostic medical device

i: Consult instructions for use

LOT: Batch / Lot code

Σ: Single use only

Use by YYYY-MM-DD: Use by Date

REF: Catalog number

CONTROL +: Positive Control

CONTROL -: Negative Control

SOL: Developer Solution

CONT: Contents

DEV: Test Device

IFU: Instructions for Use

PRO: Procedure Card

MF: Manufactured For

PIP: Sample Transfer Pipette

SWAB: Throat Swab

TUBE: Extraction Tube

EA: Extraction Reagent A

EB: Extraction Reagent B

References

1. Bisno AL. Group A streptococcal infections and acute rheumatic fever. N. Engl. J. Med. 325: 783-793 (1991).
2. Kuttner AG and Krumwiede E. Observations on the effect of Streptococcal upper respiratory infections on rheumatic children: a three-year study. J. Clin. Invest. 20: 273-287 (1941).
3. Wannamaker LW. Changes and changing concepts in the biology of group A Streptococci and the epidemiology of streptococcal infections. Rev. Infect. Dis., 2: 967-973, (1979).
4. Facklam RR and Washington JA. Streptococcus and related catalase-negative gram-positive cocci. In: Manual of Clinical Microbiology, 5th ed., Balows, A., Fausler, W.J., Hermann, K.L., Isenberg, H.D. and Shadomy, J.J. (eds), American Society of Microbiology, Chapter 29, pp. 238-257 (1991).
5. Bisno AL, Pearce IA, Wall HP, Moody MD, and Stollerman GH. Contrasting epidemiology of acute rheumatic fever and acute glomerulonephritis. N. Eng. J. Med. 283: 561-565 (1970).
6. Potter EV, Svartman M, Mohamed I, Cox R, Poo-King T, and Earle DP. Tropical acute rheumatic fever and associated streptococcal infections compared with concurrent acute glomerulonephritis. J. Pediatr. 92: 325-333 (1978).
7. American Academy of Pediatrics. Peter, G., ed. 1994 Red Book: Report of the Committee on Infectious Diseases. 23rd ed. Elk Grove Village, IL; American Academy of Pediatrics; 1994: p. 433.
8. Lauer BA, Reller LB and Mirrell S. Effect of atmosphere and duration of incubation on primary isolation of group A streptococci from throat cultures. J. Clin. Microb.

Distribution Information

Distributed by: Cardinal Health, Waukegan, IL 60085 USA

Origin: USA

© 2021 Cardinal Health. All Rights Reserved. CARDINAL HEALTH and the Cardinal Health LOGO are trademarks of Cardinal Health and may be registered in the US and/or other countries. All other marks are the property of their respective owners. Patent: cardinalhealth.com/patents.

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