Rapid Cito test Strep A for the diagnosis of streptococcal angina No. 1

Instructions for the rapid Streptotest Cito test Strep A for the diagnosis of streptococcal angina No. 1

Description

The rapid test for the diagnosis of streptococcal tonsillitis is a rapid immunochromatographic assay for the qualitative detection of group A streptococcus antigens in throat swabs for the diagnosis of streptococcal tonsillopharyngitis.

GENERAL INFORMATION

Sore throat, as a frequent symptom of acute pharyngitis and tonsillitis, is one of the most common reasons for seeking medical attention (pediatrician or family doctor) and self-medication. Usually, most cases of acute tonsillopharyngitis are of viral origin and therefore do not require the appointment of antibacterial therapy. However, a large proportion also belong to bacterial infections (about 20%), among the pathogens of which streptococcus occupies the first place.

Streptococci are gram-positive aerobic bacteria that cause a variety of diseases, including tonsillopharyngitis, pneumonia, wound and skin infections, sepsis, and endocarditis. The most significant pathogen from the group of streptococci is Streptococcus pyogenes, which is β-hemolytic and belongs to group A according to the Lensfield classification, therefore it is classified as group A β-hemolytic streptococci (GAS). It causes 5 to 15% of cases of acute tonsillopharyngitis in adults and 20-30% in children. Undiagnosed and untreated streptococcal tonsillopharyngitis can have serious complications, both purulent (pharyngeal abscesses of various localization, purulent lymphadenitis) and systemic (acute rheumatic fever, poststreptococcal reactive arthritis, streptococcal toxic shock syndrome, acute poststreptococcal glomerulonephritis).

The “gold standard” for diagnosing acute tonsillitis is the culture method of research, but it takes a lot of time, which, of course, is unacceptable in acute disease. Today, the most common method for diagnosing tonsillitis in the practice of a primary care physician in the world is the method of rapid tests, which can be performed in a polyclinic or outpatient clinic of a general practitioner with a result in 5–10 min.

The rapid test for the diagnosis of streptococcal tonsillitis CITO TEST® Strep A detects antigens of group A streptococci in throat swab samples and allows you to establish the etiology of tonsillopharyngitis at the doctor's appointment or directly at the patient's bedside, which is beneficial not only for the patient, who will be diagnosed within a few minutes and prescribed a justified antibacterial or only symptomatic therapy.

COMPLETENESS

TEST PRINCIPLE

The rapid test for the diagnosis of streptococcal sore throat is a qualitative, lateral-flow immunochromatographic assay for the detection of group A streptococcus carbohydrate antigens in throat swabs.

In this test, antibodies specific for the carbohydrate antigens of group A streptococcus are pre-coated in the test zone of the test cassette. During the study, the antigens of the clinical throat sample react with antibodies to group A streptococcus, which are coated with colored particles. The mixture then migrates along the membrane and reacts with antibodies to group A streptococcus antigen immobilized on the membrane to form a colored test line (T). The appearance of a line in the test zone indicates a positive test result and, conversely, its absence indicates a negative result. The control line (C), which always appears in the control zone of the test cassette, is an internal control of the procedure and indicates that a sufficient amount of sample has been used and the membrane capillaries have been filled.

Reservation

For professional in vitro diagnostics.

Do not use after the expiration date indicated on the package.

Do not eat, drink or smoke in the area where samples and tests are located.

When working with samples, it is necessary to use protective clothing: a gown, gloves, and goggles.

Specimens should be handled as potentially infectious material. Observe established precautions regarding microbiological risks and follow appropriate standard procedures for specimen disposal.

Used tests should be disposed of in accordance with applicable legislation.

Humidity and temperature can affect the test result.

Do not use the test if the integrity of the packaging is damaged.

Extraction Reagent 2 contains an acidic solution and should be rinsed with plenty of water if it comes into contact with skin or eyes.

Be careful when using reagents to avoid mixing up the caps for the reagent vials.

Method of application

Sample collection and preparation

1. Use the sterile swab provided in the kit to collect a swab from the back of the throat, tonsils, and other inflamed areas. Probe swabs with Stewart or Ames transport medium may also be used with this test. When using a spatula, avoid touching the tongue, inner cheeks, and teeth with the swab.

3. If it is necessary to culture the test material on a nutrient medium, gently swirl the tip of the swab in a Petri dish with blood agar selective for group A streptococci (GAS) and only then use the swab for testing with this test.

Testing procedure

Bring the test, reagents, and sample swab to 15-30ºC before testing.

1. Remove the test cassette from the pouch and use it as soon as possible. For best results, test immediately after opening the pouch.

2. Holding the Extraction Reagent 1 vial vertically, add 4 full drops (approximately 240 µl (μl)) of the reagent to the test tube. Extraction Reagent 1 is red in color. To the same test tube, add 4 full drops (approximately 160 µl (μl)) of Extraction Reagent 2 while holding the reagent vial vertically. Extraction Reagent 2 is colorless. Mix the mixture by gently rotating the test tube (Figure 1). Extraction Reagent 1 changes color from red to yellow after addition of Extraction Reagent 2 to the test tube.

3. Immediately place the swab in the tube and rotate it vigorously in the tube 15 times. Leave the swab in the tube for 1 min (Fig. 2).

4. Press the swab against the walls of the tube and squeeze it out by squeezing the bottom of the tube and simultaneously removing the swab so that most of the liquid remains in the tube. Discard the swab (Fig. 3).

5. Attach the pipette tip to the test tube. Place the test cassette on a clean, flat surface. Add 3 drops of the resulting solution (approximately 100 µl (μl)) to the specimen well (S) on the test cassette and start the timer.

Evaluate the result at 5 min. Disregard the test results after 10 min (Fig. 4 and 5).

ACCOUNTING OF THE RESULT

POSITIVE:* Two lines appear. One colored line should appear in the control region (C) and the other in the test region (T). A positive result indicates that Group A Streptococcus antigen was detected in the specimen.

*NOTE: The intensity of the line in the test region (T) depends on the concentration of Group A Streptococcus antigens in the specimen. Therefore, the appearance of a colored line of any shade in the test region (T) should be considered a positive result.

NEGATIVE: One colored line appears in the control region (C). No line appears in the test region (T). A negative result indicates that group A streptococcus antigens are absent in the specimen or their concentration is below the detection limit of the test.

INVALID: Control line (C) does not appear. Using an insufficient amount of specimen or not following the test procedure are the most common reasons for a missing control line. Review the test procedure and repeat the test using a new test cassette. If the problem persists, stop testing immediately and contact your local distributor.

Storage conditions

Store the test in a tightly sealed container at 2-30 ºC. The test is stable until the expiration date indicated on the package. Do not freeze! Shelf life 24 months.

QUALITY CONTROL

The test is equipped with an internal quality control. The colored line that appears in the control region (C) is the internal control of the test procedure. Its presence confirms the use of a sufficient volume of sample and filling of the membrane capillaries.

Technical specifications

Sensitivity and specificity

The study was conducted on 525 throat swab samples from patients with symptoms of pharyngitis using culture and rapid tests. Of the 525 samples, 401 were confirmed negative by culture and 124 were confirmed positive. The following results were obtained during the study:

Relative sensitivity: 94.4% (88.7%-97.7%)*

Relative specificity: 97.3% (95.1%-98.6%)*

Accuracy: 96.6% (94.6%-98.0%)*

*95% confidence interval

Cross-reactivity

Cross-reactivity testing of the rapid test was performed with the following microorganisms. Negative results were obtained.