Strep throat is a term used to indicate a throat infection caused by bacteria belonging to the genus Streptococcus i.e. group A Streptococcus (GAS), group A beta-hemolytic streptococcus, or Streptococcus pyrogenes.
The infection is not only restricted to the pharynx and larynx but extends upwards to affect tonsils. Being contagious, the disease can spread from person to person by droplet transfer during sneezing or coughing. Although the infection is not restricted to a certain age group, people between 5 to 15 years of age are more prone to contracting the disease.
According to the Centers for Disease Control and Prevention (CDC), the symptoms of a Strep infection include:
- Throat pain especially while swallowing
- Inflamed tonsils as well as lymph nodes in the neck region
- Reddened tonsils with visible white streaks of pus
- The appearance of petechiae i.e. reddish spots on the upper palate of the mouth
- Stomach ache
- Nausea and vomiting
- Fever (≥101°F)
Let us understand which tests can be used to make a diagnosis of strep throat.
How to diagnose strep throat?
As soon as a patient refers to a physician, a primary diagnosis of an infection is made based on the symptomatic analysis. In case of prominent strep A symptoms, the healthcare professional asks the patient to take a rapid strep test. These rapid strep tests are of multiple kinds and include the following:
· Rapid strep antigen test:
Rapid strep antigen test or rapid antigen detection test (RADT) is the first test recommended by physicians to confirm the presence of strep A bacteria. The test works by identifying the antigens of the bacterial cells. To do so, an antibody solution is used which can detect group A Streptococcus within 8 minutes. This way, a rapid strep antigen test can give results within 10 to 20 minutes.
However, when it comes to the accuracy of the results, rapid strep tests are not completely reliable as a false-negative result can be indicated. Therefore, if your physician deems fit, you can be recommended to take an additional throat culture test for confirmation. Furthermore, a positive strep antigen test manifests the presence of a bacterial infection which eliminates the need for any further testing.
· Throat culture:
Throat culture is performed the same way as a rapid strep test is done. However, in the present case, it may take 24 to 48 hours for the results to beavailable.In case of a positive result, the patient has strep A infection while a negative one indicates that the pathogen involved is other than Streptococcus bacteria.The accuracy of a throat culture is relatively higher than that of a rapid antigen test thus it is considered more reliable.
How to conduct a strep test?
In case of a throat infection, it is important to know the causative agent. If bacteria are responsible for the disease, the most suited treatment is the use of antibiotics.
However, if the infection has a viral basis, there is no need to recommend antibiotic therapy as these drugs do not work against viruses. Therefore, a confirmation regarding the pathogen is needed before starting therapy.
For both kinds of strep tests, the following steps are to be kept in mind while taking a sample:
- Ask the patient to sit down comfortably and tilt the head backward.
- Once seated, the patient has to open his or her mouth wide open.
- At this point, the healthcare professional may use a tongue depressor to increase visualization.
- A special swab is used to collect the sample which is inserted deeper into the patient’s throat until tonsils are reached.
- The collected sample is either subjected to a rapid antigen test or sent to the lab for a throat culture.
BD VeritorTM system is a rapid test kit employed for the detection of Strep A streptococcus. This product, along with other different types of test strips, is available on Health Supply 770 at great prices.
Medical equipment used for strep throat test
To conduct a strep throat test, the following testing supplies are needed:
- Tongue blade wooden depressors
- Sterile throat swabs
- Extraction reagent
- Positive and negative control
Comparison of different strep throat tests
According to a study published in the American Family Physician Journal, a comparison was made between the specificity of RADT and throat culture. The findings of the study manifested no significant difference between the two in addition to identical rates of false-negative and false-positive tests.
Moreover, it was revealed that in patients who had recently acquired a strep infection, the reliability of RADT exceeded that of throat culture. Rapid antigen detection tests as well as throat cultures can also be compared based on their working principle, cost, as well as result interpretation, parameters which have been given in the following table:
|Parameters||Rapid antigen detection test (RADT)||Throat culture|
|Working principle||Antigen-antibody reaction||Antigen-antibody reaction|
|Specificity||98 to 95%||76 to 99%|
|Sensitivity||90 to 95%||90 to 95%|
|Time to give results||18 to 20 minutes||24 to 48 hours|
|Reliability||Lower than throat culture||Higher than RADT|
|Approximation of cost per test||$15||$32|
|In case of a positive result||Strep infection is confirmed||Strep infection is confirmed|
|In case of a negative result||An additional throat culture test is often needed||Strep bacteria absent|
Pharyngitis, or as it is commonly known, strep throat is a condition caused by Streptococcus bacteria. The infection compromises the patient’s quality of life and needs to be treated. But first, it is essential to evaluate the exact cause of a throat infection which can be done by doing RADT or throat culture. The apparatus needed for both tests is very basic and does not cost much. Therefore, taking a strep test is not only quick and easy but also economical.