Strep throat is a common bacterial infection that affects the throat and tonsils. The condition is caused by the bacterium Streptococcus pyogenes, also known as Group A Streptococcus (GAS). While most sore throats are caused by viruses, a correct diagnosis of strep throat is necessary because it requires antibiotic treatment. Prompt identification and treatment are important to prevent rare but serious complications, such as rheumatic fever or post-streptococcal glomerulonephritis, which involves kidney inflammation. The diagnostic process is relatively quick and simple, relying on a throat swab to collect a sample for testing.
The Target Area for Swabbing
The goal of the strep throat test is to collect a sample directly from the anatomical sites where the Group A Streptococcus bacteria are most likely to be concentrated. The primary target areas are the tonsils and the posterior pharyngeal wall, which is the back of the throat. The tonsils are masses of lymphoid tissue located on either side of the back of the throat.
In a person with strep throat, these areas often show visible signs of infection, such as redness, swelling, or the presence of white or yellow patches of pus. Swabbing these specific locations ensures the healthcare provider collects enough of the bacteria to yield an accurate result. Collecting the specimen from other parts of the mouth, such as the tongue or gums, can lead to a false negative result.
The Swabbing Procedure
The collection of the throat swab sample is a quick process that typically takes only a few seconds. The healthcare provider will first have the patient open their mouth widely and tilt their head back slightly to better visualize the back of the throat. A sterile tongue depressor is often used to gently hold the tongue down, allowing for an unobstructed view of the tonsils and the pharynx.
Once the area is visible, a sterile swab is carefully inserted into the mouth, avoiding contact with the tongue, cheeks, and teeth to prevent contamination of the sample. The swab is then firmly rubbed against the surface of both tonsils and the back wall of the throat. This motion is necessary to collect the organisms adhering to the surface of the throat tissue.
The patient may experience a brief gag reflex when the swab touches the back of the throat, which is a normal response. Sometimes, two separate swabs are collected during the single procedure; one is used for a rapid test, and the second is reserved for a throat culture if needed. Immediately after collection, the swab is placed into a sterile transport tube to preserve the specimen for laboratory analysis.
Preparing for the Test and Result Timeline
There is generally no significant preparation required for a strep throat test, but a few actions can help ensure the accuracy of the results. Patients should generally avoid using mouthwash or gargling immediately before the test, as these products may reduce the number of bacteria present on the throat surface and potentially interfere with the test. It is also important to tell the healthcare provider if any antibiotics have been taken recently, as this medication can also lower the bacterial count and affect the test outcome.
Two main types of tests are used to analyze the swab sample, each with a different timeline for results. The Rapid Strep Test, also known as a Rapid Antigen Detection Test, can detect Group A Strep proteins and often provides results within 10 to 30 minutes, allowing for immediate treatment decisions. While quick, the Rapid Strep Test is not as sensitive as a culture and can sometimes produce a false negative result.
If the rapid test is negative, especially for children and adolescents, the healthcare provider may send the second swab for a Throat Culture to confirm the result. A throat culture is considered the most accurate method and works by allowing any bacteria present to grow in a laboratory dish. This process takes longer, with results typically becoming available within 24 to 48 hours.