Patient is taking to his doctor

The COVID-19 pandemic has raised a range of questions relating to the accuracy of diagnostic tests, further fueled by the introduction of surge-driving SARS-CoV-2 variants. A test result you can trust is of great value and a well-known benefit, but understanding what factors contribute to that result’s reliability is more complex.

One key measure that affects a COVID-19 test’s accuracy is the amount of SARS-CoV-2 virus it can detect, or its limit of detection (LoD). A test’s LoD equates to the lowest detectable concentration of virus that can be identified consistently within a sample using that test. Here’s everything you need to know about how a COVID-19 test’s reliability directly relates to this key measure.

If someone has COVID-19, will the test being used detect it?

An important differentiator between COVID-19 tests is analytical sensitivity. A highly sensitive test has a lower LoD, meaning it can detect SARS-CoV-2 even when there’s only a small amount of virus present in the patient sample. A test’s analytical sensitivity is especially important when identifying infectious patients who may have a lower viral load, including those recently infected with a viral load that has not yet peaked. According to one study, viral load for omicron patients is highest three to six days after diagnosis or symptom onset [1].

What are the personal and public health benefits of a COVID-19 test that can detect SARS-CoV-2 at lower levels?

Because quick identification of cases can help those who are infected quarantine sooner, sensitive tests that are more accurate early in infection offer a range of public health benefits. Consider the possible implications of using a test that’s unable to detect SARS-CoV-2 at low levels: You could wake up tomorrow morning with a sniffle, take a less sensitive test and get a negative result. Feeling safe to be around others, you drop your kids off at school, head to work, and run a few errands. Then, you start feeling worse, and get tested again. You then learn you have COVID-19 and begin to quarantine. A more sensitive test could have led to quarantine before going out in public and exposing others to the virus.

From a clinical perspective, an earlier diagnosis of active infection could also be important when it comes to initiating treatments.

How do COVID-19 tests compare when it comes to analytical sensitivity?

While lab-based PCR is available for COVID-19 testing, there are instances when a faster turnaround time is necessary or more convenient. Rapid test options, including antigen and PCR, are available to fulfill this need.

LoD offers a quantitative measure of analytical sensitivity that can be compared across tests. Rapid antigen tests generally have higher LoDs and are less sensitive than rapid PCR options [2]. And among commercially available rapid PCR tests, there are notable differences in LoDs and analytical sensitivity, as well.

When comparing rapid PCR options, Thermo Fisher Scientific’s Accula SARS-CoV-2 Test has a reported limit of detection among the lowest measured for the FDA SARS-CoV-2 Reference Panel [3], providing results in approximately 30 minutes. With its compact design, the Accula System consists of the Accula Dock and Accula Test Kit. The dock plugs into a standard wall outlet and does not require long initialization steps to begin testing, making set up easy and allowing for testing to be performed in areas where testing space may be limited.

What does a highly sensitive rapid RT-PCR test mean for the pandemic?

As COVID-19 case counts have fluctuated, rapid, sensitive tests have played an important role in restoring normal ways of life. From helping to protect students in schools to preventing virus spread at large events, rapid RT-PCR offers a fast, reliable test option with much-needed flexibility. And faster negative results have value, too. Someone who isn’t feeling well but might just have the common cold can confirm COVID-19 status and resume regular activities within the hour, versus potentially having to wait days for results.

Our recent case studies have showcased how schools, pharmacies, urgent care clinics, travelers and event organizers are turning to rapid PCR given its convenience and sensitivity. To learn more, visit our Accula SARS-CoV-2 Test page or contact us to request a quote.

Other articles

1. Torjesen I. Covid-19: Peak of viral shedding is later with omicron variant, Japanese data suggest. BMJ. 2022 Jan 13;376:o89. doi: 10.1136/bmj.o89. PMID: 35027360.
2. What Is an Antigen Test?
3. SARS-CoV-2 Reference Panel Comparative Data.US FDA. Content current as of 12/07/20.

Disclaimer: This Accula SARS-CoV-2 Test has not been FDA cleared or approved but has been authorized for emergency use by FDA for use by laboratories certified under the Clinical Laboratory Improvement Amendments (CLIA) of 1988, 42 U.S.C. §263a, that meet requirements to perform high, moderate, or waived complexity tests. The test is authorized for use at the Point of Care (POC), i.e., in patient care settings operating under a CLIA Certificate of Waiver, Certificate of Compliance, or Certificate of Accreditation. This test has been authorized only for the detection of nucleic acid from SARS-CoV-2, not for any other viruses or pathogens. The emergency use of this test is only authorized for the duration of the declaration that circumstances exist justifying the authorization of emergency use of in vitro diagnostics for detection and/or diagnosis of COVID-19 under Section 564(b)(1) of the Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 360bbb-3(b)(1), unless the declaration is terminated or authorization is revoked sooner.

For Use under the Emergency Use Authorization (EUA) Only. For prescription use only. For in vitro diagnostic use.

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