Strep throat, caused by the bacterium Streptococcus pyogenes (Group A Streptococcus or GAS), is a common bacterial infection affecting the throat and tonsils. It can lead to a sore throat that often comes on quickly and can be quite painful. Accurate and timely diagnosis is important for appropriate treatment, preventing spread, and avoiding potential complications like kidney inflammation or rheumatic fever.
Understanding Strep Tests
Two types of tests diagnose strep throat: Rapid Antigen Detection Tests (RADT) and throat cultures. A rapid strep test detects antigens from Group A Streptococcus bacteria directly from a throat swab. This test provides quick results, often within minutes, making it a convenient option for initial screening. However, rapid tests may not detect all strep infections, with a sensitivity around 85-86%.
In contrast, a throat culture involves taking a swab sample and allowing bacteria to grow on a special plate in a laboratory. This method is highly accurate and can sometimes identify infections a rapid test might miss. The main drawback is the time required for results, which typically takes 24 to 48 hours. Healthcare providers often use rapid tests first and may follow up with a throat culture, particularly for children and teenagers, if the rapid test is negative but strep throat is still suspected.
Preparing for a Strep Test
Before collecting a throat swab for an at-home strep test, gather all necessary supplies. You will need the strep test kit, which typically includes a sterile swab and reagents. Additionally, have a tongue depressor, a light source, disposable gloves, hand sanitizer, and a bag for waste disposal ready. Proper preparation helps ensure both hygiene and an effective sample collection.
Preparing the individual for the test is important, especially if testing a child. Explain the procedure calmly to help them understand what to expect and encourage them to relax. Ensure the testing area is well-lit for a clear view of the throat, and position the person comfortably, perhaps with their head tilted slightly back. Wash your hands thoroughly with soap and water or use an alcohol-based hand sanitizer before donning gloves.
Step-by-Step Strep Swab Collection
Begin the collection process by washing your hands thoroughly and putting on disposable gloves to maintain hygiene and prevent contamination. Carefully open the strep test kit and remove the sterile swab, taking care not to touch the soft tip. Have the person open their mouth wide and, if necessary, use a tongue depressor to gently press down on their tongue, which helps provide an unobstructed view of the back of the throat and tonsils.
Direct the swab tip towards the tonsillar area and the back of the throat, aiming for any red or inflamed areas or visible white patches. Gently but firmly rub the swab across both tonsils and the posterior pharyngeal wall using a back-and-forth motion to collect a sample. Avoid touching the swab to the tongue, teeth, cheeks, or gums, as this can contaminate the sample and affect the accuracy of the test results. Once the sample is collected, carefully remove the swab from the mouth without touching other surfaces.
Interpreting and Acting on Results
Immediately after collection, process the swab according to the instructions provided with your at-home test kit. Most rapid tests involve immersing the swab in a reagent solution, rotating it to extract bacteria, and then inserting a test strip or cassette. The test strip will display lines to indicate the result within 5 to 10 minutes. A positive result shows two colored lines, while a negative result displays only one control line.
It is important to follow up with a healthcare professional regardless of the result. If the rapid test is positive, a healthcare provider can prescribe antibiotics to treat strep throat and prevent complications. If the rapid test is negative but symptoms persist or are concerning, especially for children and teenagers, a healthcare provider may recommend a throat culture for confirmation. After testing, dispose of all used materials, including the swab, reagents, and test kit components, in a sealed waste bag as potentially infectious waste, following local guidelines.