This note was translated into Spanish and edited for clarity from a English Version.
An investigation that the news agency ProPublica unveiled last month generated various reactions after thoroughly reporting how Northshore Clinical Labsa politically-linked COVID testing company in Nevada, provided flawed tests that missed 96 percent of positive cases.
To better understand the details of testing and some of the process that labs perform, we recently interviewed Nevada State Public Health Laboratory Director Mark Pandori, who provided recommendations for storing COVID tests at home (in the fridge! !) and processes related to the various testing methods.
The vaccines and COVID-19 tests are still available and also they can be ordered free of charge through the US Postal Service.
This is part of the interview:
What are rapid antigen tests and PCR tests? How do they work?
Antigen tests, or rapid tests, detect specific protein fragments of the coronavirus. After you take a swab of fluid from your nose and use it in the test, the fluid binds to the chemicals in the test. When the fluid binds, there is a chemical reaction that produces a line that indicates whether fragments of the virus are present or not.
On the other hand, a PCR test looks for a specific genomic sequence that is unique to SARS-CoV2. The PCR test is considered the gold standard for detecting the virus. It is designed to detect the specific RNA (or genetic material) of the virus and can detect it within days of infection, even in people without symptoms.
How do health professionals collect and prepare a sample for testing? What can go wrong during the process?
Like the rapid test, a swab is inserted into the nose and then placed in a tube of fluid that stabilizes the sample. When the sample arrives at the lab, researchers can test it to see if it contains the virus.
What can go wrong? At the time of collection, if someone is quick, they may not get a good specimen. If it’s a lousy system, someone can mix two samples. They could also collect the sample correctly, but jeopardize the integrity of the result if they leave it out in the sun for too long or don’t get it to a lab within a reasonable time.
These tests are biochemical, and like all the biochemical crap in your fridge, it goes bad over time and passes faster when not cold.
How long can a sample last after it has been collected?
Using liquid storage methods, the sample can remain at room temperature for probably eight to 24 hours. But then refrigeration is needed, preferably within eight hours. It can then be at refrigeration temperature for 72 hours. Then it must be proofed or frozen below 80 degrees Fahrenheit. And once frozen, it’s practically indefinite.
What can go wrong with a home rapid test? What should be paid attention to if people have rapid tests at home?
Pay attention to the expiration date. These tests have chemicals and antibodies in addition to proteins. Just like anything else left out at room temperature, they go bad. And if they break down, they will lose capacity, specificity and sensitivity.
If you have been storing it at an extremely hot temperature, I would be concerned that it would speed up the decomposition of the chemicals in those samples.
What are some common reasons why a lab may get an incorrect result even after they have passed the licensing requirements?
Laboratories are generally the best at keeping samples at the correct temperatures. It is rare that there is a reason to fail in a lab.
Laboratories work with 96-well plates that are 5 inches by 3 inches in size. When the technicians are using those pipettes in those wells, if there’s any splashing and they don’t realize it, that could cause a false-positive reaction. Many times lab samples get mixed up because they are running thousands of samples in a row. Those would be the most common errors that lead to an incorrect result.
We don’t see the test itself fail very often. Usually this would be caused by operator error.
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