Coronavirus Testing as at March 2020

Covid-19 Diagnosis Test

Currently the only FDA-approved test to diagnose a COVID-19 disease in the United States uses PCR test technology to detect COVID-19 nucleic acids. It is a sophisticated test method which uses a nasal or throat airway sample collection. It is very sensitive and specific and can diagnose an early infection to COVID-19 virus. However, if you are not collecting a test sample during the time that the virus is replicating, 60% of the positive cases will be missed.

Expanding Testing

With a need to understand the larger picture of COVID-19 exposure, the FDA has implemented an Emergency Use Authorization (EUA) which allows CLIA certified labs (who meet a certain criteria) to submit to FDA and continue to market their tests pending full FDA approval.

Antibody Testing

The latest of these EUA approved tests are antibody tests. Antibody test results cannot diagnose COVID-19 disease, but may prove useful to determine a prior exposure that was otherwise asymptomatic, missed or not tested for when active.

What tests are available?

There are three COVID-19 immunoglobulin (Ig) or antibody tests available – each will test for IgA, IgM, and/or IgG antibodies. The majority of labs are using IgM/IgG or IgG only tests. For this reason, we will focus on these two tests. Additional testing is also being developed using other antigen-antibody responses.

Antibodies are produced in response to an antigen associated with the COVID-19 virus. Most antigens are proteins and current tests will look at an antibody response to either the COVID-19 Spike (S) protein, Membrane (M) protein or the NucleoProtein (N) protein.

Each of these proteins also has a different level of specificity and sensitivity to the COVID-19 virus. Ranking in order of most to least sensitivity; the most sensitive has the strongest response to IgG :

N protein is the most sensitive and greatest response
M protein
S protein produce the weakest responses

You also want the lab’s testing methods to be as specific as possible to the COVID-19 virus. This means the antibody test is less likely to cross-react with another non-COVID-19 coronavirus or influenza virus.

When does the body produce antibodies?

After the COVID-19 incubation period of approximately 14 days, the body will first start producing IgM antibodies to the N, M, S proteins. IgG antibodies will be produced later.
The antibodies to the lgM N protein will be detectable within 3-5 days and will commonly peak within 10 days before declining around 20 days.
The IgG response to the N protein will be detected within 5-7 days and will commonly peak within 20 days before declining around day 30.
The IgM response is typically associated with fighting an early infectious exposure and the IgG response with longer term protection.

What does having antibodies mean, am I immune? At this time long-term immunity has not been validated. There is a lot about the COVID-19 immune response that we don’t know yet. We do know plasma containing antibodies from a patient who has recovered from COVID-19 has been used to treat a patient with an active COVID-19 infection The antibody test could also help identify potential plasma donors to treat this deadly disease.

Where can you get the antibody test?

The following labs are offering COVID-19 antibody tests. All three have FDA EUA approval and have been chosen for their price point, availability, sensitivity and specificity. Each lab also requires a healthcare provider to order the patient test and follow-up with any necessary recommendations. NOTE: We do not recommend ordering a non-approved COVID-19 antibody test online.

IgG/IgM Testing

No cross-reactivity with other coronaviruses or flu viruses.

Blood draw required

Patients can submit to in-network insurance or $70 for IgG/IgM or $35 for either IgG or IgM

Only using Blood Stat Express – mobile phlebotomy for blood draws- $35 fee in OC or $45 fee in South LA

Offers two IgG/IgM tests. Tests N protein antibodies
No cross-reactivity with other coronaviruses or flu viruses

Serum test requires blood draw - $150; has a network of 6000 mobile phlebotomists $100 fee for first patient, $50 for any additional patient

At home Finger-prick test – Cost $150

IgG only

Possibility of cross-reactivity with other coronaviruses

Blood draw required at a Quest lab site.

Patient must be asymptomatic and will be screened at lab.

Due to the CARES Act, Quest will accept any in-network or out-of-network insurance or any uninsured patient for this test. No patient will be required to pay any out-of-pocket expense for this test

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Coronavirus Testing as at March 2020