Rapids vs. Lab Tests for Corona Virus
We've all heard mixed messages throughout the pandemic, but one that we continue to get asked is "Are rapid tests for Covid-19 reliable?" The answer is, it depends. It depends on what type of rapid test it is.
Because of the dynamics of this pandemic and the speed with which new testing was authorized under the FDA's emergency use program, we are seeing testing sites offering a variety of rapid tests and all are not created equal (or even in the same league)! There are 3 main types of Covid-19 tests on the market --- PCR tests, Antigen tests, and Antibody tests. All 3 have rapid (or instant) testing platforms and lab based platforms. So, when you call around looking for a 'rapid test,' a clinic might say they have them, but when you arrive, the test is a rapid antibody test, not the rapid PCR that you really need if you are looking to confirm or rule out Covid-19 infection.
Let's take a brief look at each of the 3 types of tests.
Antibody tests - These are useful for showing evidence of past infection. Rapid versions are often finger prick tests and the lab sample is a blood draw. The rapid versions of these tests were some of the first to market under the EUA and many were highly unreliable. There are a few diamonds in the rough, and most of the unreliable options did not complete the EUA requirements and exited the market in spring/summer, so those remaining are a decent option for a quick and easy way to see if you have antibodies in your system.
Antigen tests - These are the newest entry to the market and many clinics and doctors' offices are using these as a first line of defense to check for Covid-19 infection. These tests detect antigens from SARS-CoV-2. While they are highly sensitive, because the amount of antigen in your system generally is highest in the early period of infection and it decreases from there, they aren't as effective as the PCR test. The antigen test is NOT a diagnostic test, so a negative result should be taken lightly, and followed up with a PCR test if indicated based on exposure and/or symptoms.
PCR tests - PCR (also called molecular tests/assays/RT-PCR) tests provide the highest level of reliability, but all PCR tests are not the same. Rapid tests such as those done on the Abbott IDNow or the Cepheid system are slightly less reliable than their lab-based counterparts; however, all are in the 94-98% range. And, there are times when a rapid result is necessary and can go along way in slowing the spread of this virus. The RT-PCR test is the test type required for travel, schools, pre-operative clearance, and for most employers doing testing.
It's all in knowing what these different options are and what situations to apply them in. Your healthcare provider should be able to answer questions about the various options and to explain to you why a particular one is being recommended based on your situation. You can always call or message us here for questions too.