If you or a family member have ever visited a doctor for a sore throat, more than likely you’ve had a Rapid Strep Test performed. Historically a medical professional or technician swabs the throat with a long cotton swab and obtains a sample. Approximately 5 minutes later they inform you about the results. Behind the scenes they bring the sample into another room or a lab and put it in a small plastic tube filled that must first be filled with a few drops of acetic acid and sodium nitrite and a test strip. Once this is left for 5 minutes, the test strip with show either one line (negative for strep throat) or two lines (positive for strep throat).
How does the test work?
For the scientists in the audience most of the current Rapid Strep Tests use lateral flow technology. The sample on the cotton-tipped swab is applied to a strip of nitrocellulose film and, if Group A strep antigens are present, these will migrate along the film to form a visible line of antigen bound to labeled antibodies. The test is about 95%-99% specific (Positive Rapid Strep Test means that you are 95%-99% likely to have strep throat) and 70%-90% sensitive (If you have strep throat, the test will be positive 70%-90% of the time).
What are the consequences of incorrect results of the Rapid Strep Test?
Well in the rare instance where the test is falsely positive (the test is positive when you really don’t have strep), the most likely scenario is that you would have been placed on antibiotics unnecessarily. Unless you have an allergic reaction or adverse drug reaction to the antibiotic, this is unlikely to cause any harm. On the other hand, if you have a false negative test (you have strep throat, but the test is negative), there could be potential consequences if left untreated. After about 9 days of untreated strep throat, the risk of rheumatic fever begins to climb, and irreversible heart damage may occur. Kidney damage may also result if strep throat is left untreated.
Now that you understand the sensitivity and specificity of the test, you might be wondering what can be done to improve those numbers. The most important thing is to make sure that you first obtain a good sample on the swab. If the patient has difficulty tolerating the swabbing of the throat, the sample may be inadequate. Additionally, the combination of the results of the Rapid Strep Test paired with the experience of a trained health care professional results in a much higher sensitivity and the chance of leaving strep throat undiagnosed or misdiagnosed drops considerably.
At Physician 360, we are the first to bring Rapid Strep Testing to the home, using the combination of an already proven tester with the experience of board certified physicians. Stay tuned for future developments as we are currently working on the first truly one-step Rapid Strep Tester designed to simplify the process and increase sensitivity when compared to currently available testers.
Written By: Dr. Rob Lapporte