September 18, 2020

How Do Rapid Strep Tests Work?


A new video has been made describing how a rapid strep test is performed. Not only is the procedure explained, but also how the testing itself is carried out to determine whether a patient is strep test positive or not. For those inclined, the science behind rapid strep testing is described at the latter half of the video. Hint! It's called a lateral flow assay incorporating both rabbit and goat antibodies!

Rapid strep test kits can be purchased by anybody to be done at home which may save parents/patients a lot of money in doctor visits for those prone to strep infections. Indeed, should a rapid strep test be positive, than you know that a doctor's visit is definitely worthwhile. (A doctor visit may still be worthwhile since a sore throat may be due to something else like canceraphthous ulcersinus infectionreflux, etc).

Such home kits (which in fact are the same kits used in medical offices) can be purchased online through Amazon. The price is surprisingly affordable at around the cost of a single copay ~$40 to do 25 tests. There is also a rapid mono test kit that is available to purchase for around the same price as well as a rapid flu test kit.

However, with the purchase of such DIY kits, there are some pitfalls patients should be aware of if they decide to proceed. For those who have done laboratory benchwork, the directions are reminiscent of performing a chemical experiment. 

1) Perform the internal controls that come with the kit!!! The kit may be a dud and needs to be tested against itself to ensure accurate results whether negative or positive. If the controls do not work, throw the whole test kit out and buy another.
2) You must follow the directions precisely, otherwise the test results will be unreliable. In other words, if the directions call for 4 drops, than it MUST be 4 drops (not 3 drops or 5). If directions state to wait 4 minutes... you must wait exactly 4 minutes. This literally is like precision baking.
3) The test strips need to be kept in protected, sealed bag and used immediately after taking one out, otherwise the test results will be unreliable.
4) When swabbing the throat, you MUST get the cotton tip on the tonsil and/or back wall of the mouth which than must be rubbed around a couple times. Getting the tongue or cheek will increase the risk of a false negative. As such, it may be worthwhile to invest in some tongue blades to help push the tongue down in order to perform this test properly.

Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids.

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