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Best COVID Tests, Accuracy, Where to Find & More -- Boy Getting COVID Test


These are great questions, as many people want to know if they are currently infected or have already been infected with coronavirus that causes COVID-19 and have developed antibodies due to immune response. There has been much confusion and about tests for coronavirus and the FDA has reported that some test developers have falsely claimed their tests are FDA approved or authorized and that many commercial tests are performing poorly, so it is important to sort out the facts. The information in this field has been changing rapidly. Before using any test or service discussed below, confirm the information with the provider and/or other reliable information source.

Before we get into specifics, let's start with a quick overview of the types of tests for coronavirus.

Types of COVID-19 Tests

There are basically two types of tests for the coronavirus that causes COVID-19:

Virus test
This test detects the virus (SARS-CoV-2) to determine if you have an active infection and are infectious, i.e., you can spread the virus. Although you can be infectious before showing any symptoms, the virus is best detected during the first week of symptoms (which is about two weeks after becoming infected from exposure) (Sethuraman, JAMA 2020).

The virus test is best done by collecting a sample of mucous from a swab (typically from the nasopharynx or nostril) or saliva. There are two type of virus tests: the PCR and antigen test. Both tests need to be analyzed in a laboratory or with a special rapid, portable machine.

The PCR test uses a technique that amplifies genetic material (RNA) from the virus. This can take as little as a few minutes or several hours. The FDA has begun allowing some at-home sampling kits to be sold by which you can collect your own sample and drop it off or mail it to a lab, which will report the results back to you.

An analysis of tests performed among symptomatic and asymptomatic patients at Vanderbilt University Medical Center showed that the proportion of samples testing positive on PCR tests were twice as high at 2 pm than in the morning, decreasing later in the afternoon and evening. Researchers proposed this may indicate that test accuracy varies by time of day and could have public health implications (McNaughton, medRxiv 2021 -- preprint).

Update: In addition to the many commercial PCR tests that have received Emergency Use Authorization from the FDA, the CDC has been producing its own, FDA-authorized, PCR test. More recently, the CDC developed a newer test that can simultaneously test for and distinguish between COVID, influenza A and influenza B, and, as of January 1, 2022, it will withdraw the older test. Sign in to find out why.

The other type of virus test is the antigen test. It identifies a protein (or "antigen") that is specifically found on the virus. Advantages of the antigen test are that it can provide results in just 15 minutes and can be produced at lower cost, lending itself to wider use in screening. In addition, only a nasal swab is needed from the nostrils, not a much deeper, nasopharyngeal swab. The downside with antigen tests is that they are more likely to provide a false negative result than a gene amplification test; that is, it's more likely to identify your sample as negative when you are actually positive. Consequently, negative results from an antigen test may need to be confirmed with a gene amplification test — but a positive result is highly likely to be accurate. False negatives may also occur with emerging viral variants, as has been shown with some popular antigen tests that look only nucleocapsid antigen and not spike protein antigen.

Antigen tests authorized by the FDA include the Sofia 2 SARS Antigen FIA from Quidel Corporation, the BD Veritor System for Rapid Detection of SARS-CoV-2, the LumiraDx SARS-CoV-2 Ag Test, and the Abbott BinaxNOW COVID-19 Ag Card. The first three require equipment to be read, but the Abbott test is simply a card. There appears to be a significant difference in the accuracy of these tests. [Sign in for our comparison of the accuracy of antigen tests.]

Antibody test
This test detects antibodies to the virus and requires blood — either a drop or a vial — to determine if you have been infected in the past and have developed some level of immunity. This test (also called a serology test) can be run in a laboratory or on a test strip, although even test strips must be used in an authorized facility, not at home.

As it takes time to develop antibodies that can be detected, antibody tests are most accurate when performed at least 20 days after the first disease symptoms and may be most accurate (in terms of not missing antibodies that are present) 4 months or longer after a positive virus test. This was shown in study of 486 COVID patients in California in which the likelihood of a positive antibody (IgG) test result increased with time after a positive virus test. Antibody tests were most accurate (~80%) among those ages 40 to 59 years and least accurate (~65%) among those 70+ or under 40. The tests were more accurate for men than women (79% vs 72%) (Vashisht, JAMA Netw Open 2021).

Tests focus on levels of the antibody IgG, which persists without much decline for several weeks, but may include levels of IgM which fall off more rapidly (Sethuraman, JAMA 2020). These tests look for antibodies to specific parts of the virus, namely its spike proteins (proteins on the outside of the virus that can bind to receptors on human cells) or nucleocapsid proteins (proteins inside the virus). An advantage to testing for antibodies to the nucleocapsid is that these antibodies can be easier to detect, however, antibodies to the spike proteins are believed to be more important in conferring immunity against the virus, as these antibodies may block viral entry into cells — although antibodies to nucleocapsid proteins may still serve as proxies for immunity. See Finding the Best COVID-19 Test — Antibody Test to learn which marketed tests target each protein.

Although it is not recommended that antibody tests be relied upon to determine the effectiveness of vaccines, be aware that only tests that focus on antibodies to spike protein would be useful for this purpose because the authorized vaccines generate antibodies only to spike proteins. A negative result on a nucleocapsid antibody test provides no information about the effectiveness of a vaccine although it would suggest that a person has not had COVD-19. The list of authorized antibody tests below indicates whether a test focuses on spike, nucleocapsid, or both types of proteins.

If, at some point, tests for spike protein antibodies are indicated for assessing antibody response to COVID-19 vaccines, those that provide a quantitative or semi-quantitative measurement, will be more useful than those that provide only a yes/no answer. Sign in for more information about antibody tests that focus on the spike protein and are semi-quantitative, including one that is available from a major U.S. laboratory.

Note: Avoid taking large doses — 10,000 mcg or more — of biotin (a B vitamin) for several days before an antibody test, as biotin may skew results.
Sign in to learn which tests may be affected by biotin.

Another way our bodies fight the virus is with T cells. Preliminary research suggests that even if antibody levels are too low to be detected, people previously infected with the virus may produce enough T cell response to provide immunity (Sekine, MediRxiv 2020). However, currently authorized tests do not measure this type of immunity, and one should still apply distancing and health precautions regardless of test results.

Some labs may provide you with an index value that reflects the strength of the antibody signal produced from your test. Higher antibody levels generate higher signals and higher index values. The interpretation of these index values depends on the test used. For example, for a particular test the cut-offs could be "less than 1.01" for negative, "1.01 to less than 1.21" for indeterminate, and "greater than or equal to 1.21" for positive (Theel, J Clin Microbio 2020). Or, there could just be a single cut-off index value of, say, 1.40 for positive, with anything below being negative (Example: Abbott Alinity -- If you would like to know your index value, be sure to check that the lab you use provides the value.

Who is checking these tests?
To speed the availability of tests, rather than put these through its normal approval process, the FDA has provided a special emergency use allowance (EUA) for tests that, although imperfect, may be useful at this time. So there are actually no FDA "approved" SARS-CoV-2 virus tests, but a list of "FDA authorized" tests. The FDA allowances are based on data submitted by the test manufacturers, but the National Institutes of Health (NIH) and other government laboratories are now conducting independent tests of these tests and the FDA has been making the results public (see results in the Finding the Best COVID-19 Test section and watch for further announcements in our newsletter.)

Several other organizations around the world have been testing the test and/or certifying virus and antibody tests. The European Union's has been certifying tests, conferring on them its CE (Conformité Européenne) mark, and the Chinese National Medical Products Administration (NMPA) has been doing the same. Researchers in California, Denmark, and elsewhere have been testing the antibody tests. 

Be aware that in June 2020 the FDA warned consumers about at-home antibody tests being sold without FDA clearance or approval and issued warning letters to three companies selling these tests. Some of these tests were falsely labeled as FDA approved. [Update (August 19, 2020): The U.S. Department of Health and Human Services (HHS) announced that CLIA- certified laboratories are no longer required to notify the FDA, nor request its authorization, for tests they develop in-house. It is not clear what information about such tests will be maintained or published. This change could allow for novel tests to become available more quickly but eliminates oversight by the FDA, creating more of a buyer-beware situation. Labs may, voluntarily, still choose to apply to the FDA, and the FDA will continue to publish information about tests submitted this way. If in doubt, ask your doctor or lab if the test you are considering is authorized for use by the FDA. (Links to the FDA information are provided in the Finding the Best COVID-19 Test section.

Where to Get COVID-19 Tests

Virus Test
To date, the FDA has permitted the use of over 90 virus tests. The vast majority must be performed on a sample collected in a medical setting, such as in a doctor's office, a diagnostic laboratory, or a drive-through facility, but the FDA has also begun authorizing at-home sample collection tests for the virus.  

Local testing (often free)
Although you can ask your doctor for a virus test, you may be able to arrange to get a virus test for free from your state or local government. You can also go to a diagnostic laboratory or testing center, including some pharmacies. The test may be covered by your insurance or the government based on an assessment of your risk level. Here are some examples of testing programs around the country.

  • Project Baseline works with community based screening programs in locations in several states to offer free virus testing. You must fill out an online questionnaire and be accepted. You will then be given an appointment at local testing center where a sample will be collected with a self-nasal swab or a nasopharyngeal swab. The project is sponsored by the parent company of Google through its health unit, Verily, and a Google email account is needed to complete questionnaire online.
  • Rite Aid Pharmacies in some locations are participating in Project Baseline, providing testing at no cost to anyone 18+ years of age.
  • CVS (including MinuteClinic and HealthHUB) had originally offered drive-up, rapid testing using the Abbott ID NOW system, a small, portable device that yields results in 13 minutes or less. Unfortunately, this system was been reported to yield a high percentage of false negative results due to lower sensitivity than other systems. That is, a negative result may need to be confirmed using another test (Basu, bioRxiv 2020 preprint). (For more details, see Finding the Best COVID-19 Test, below). Virus testing is still offered, but specimens are now sent to independent, third-party labs for processing, and test results are available in approximately three to four days.
  • Walgreens offers drive-up testing in which you perform your own nasal swab. You sample is sent to a laboratory and you are notified by email or phone when results are available. (Originally results were promised within 24 hours).
  • Kroger Health offers public drive-thru and walk-up COVID-19 testing.

At-home tests
The FDA has authorized several fully self-administered virus tests (providing rapid results) or test kits (to be sent into a lab) for use at home. Currently, one of these (Abbott BinaxNOW Antigen Self-Test) can be purchased at pharmacies and takes 15 minutes, but be aware that it will not provide you with a digital Navica pass for events and airlines. You need to purchase the test online (at about twice the cost) if you want a digital pass. Sign in for details about the five current at-home tests.

Antibody Test
As with virus tests, many laboratories have received FDA approval to conduct antibody tests, some of which are very accurate. Although the FDA has not approved or authorized rapid, home tests for antibodies, many such tests are available in other parts of the world and some have been sold in the U.S. The FDA has authorized one rapid antibody test for use at point-of-care settings, i.e., non-laboratory medical settings such as in medical offices and pharmacies.

Through a local healthcare provider
Your healthcare provider can arrange for you to get an antibody test if deemed appropriate. Blood would be drawn either by your provider or at nearby diagnostic laboratory. Similarly, many walk-in, urgent care centers can arrange for you to have the test, for a fee, which may be covered by your insurance. The samples are typically sent to a commercial laboratory, so results can take a few days. 

Consumer-initiated testing
Be aware than in many cases, the cost of antibody tests may be covered by insurance if ordered by your physician or health care provider. Some labs will require payment for consumer-initiated tests, while others will bill your insurance. Be sure to check the payment policy of the lab you plan to use if requesting your own test. You can also check if your insurance company covers COVID-19 testing. Medicare often covers the full cost of COVID-19 virus and antibody tests. If you are uninsured, health care providers can submit a claim to have virus and antibody tests covered by the Families First Coronavirus Response Act.

QuestDirect allows consumers to request a COVID-19 IgG antibody test and pay for it online ($119 plus a $10.30 physician oversight fee). An appointment is made for a blood draw at one of Quest Diagnostics 2,200 patient service centers and test results are available online one to two days later. Interested consumers must not have experienced symptoms of COVID-19 for at least 10 days. Quest has stated that the testing will initially rely on antibody tests run on the Abbott Architect and EUROIMMUN systems.

Labcorp also allows consumers to request a test directly through its website. According to the website, there is no up-front out-of-pocket cost for consumer initiated tests, but you will be charged a $10 fee for physician oversight services (there is no physician oversight fee if the test order comes directly from your own physician or healthcare provider). Labcorp will "bill the cost of the COVID-19 IgG antibody test directly to your insurance carrier, or if uninsured, to the appropriate government program." Antibody tests offered by Labcorp include Abbott SARS-CoV-2 IgG, Roche Elecsys Anti-SARS-CoV02 (IgG), and DiaSorin SARS-CoV-2. 

You can see how each of these tests compare in the Finding the Best COVID-19 Test section below.

Rapid, home tests
The FDA has not yet approved or authorized of the use of any rapid, home antibody tests but several have been approved by the European Union, which provides its CE mark (Conformité Européenne) and/or by the Chinese National Medical Products Association (NMPA). In addition, research groups have been evaluating these tests. Some of these tests have been marketed in the U.S. without FDA approval or allowance. 

Finding the Best COVID-19 Test

There are now more than 90 virus tests (including a recently approved saliva test) and 22 antibody tests for COVID-19 authorized by the FDA. ConsumerLab has reviewed the data on their performance and assessed which appear to be the best antibody tests for COVID-19. We've added this information for ConsumerLab members. Sign in as a member or become a member now to learn how specific brands of virus and antibody tests compare, which currently appear to be the best, where to get them, and whether any of the tests can identify which variant caused an infection.

What Does a Negative Antibody Test Mean?
If you took a coronavirus antibody test and it came back negative, it can mean one of several things:
  • The test was not sensitive enough to detect antibodies that existed. This is more likely if the test had a sensitivity of less than 100% (see Finding the Best COVID-19 Test — Antibody Test for sensitivities of FDA-authorized tests);
  • You may have never had COVID-19;
  • You took the test too early -- generally less than 20 days after first disease symptoms, although, according to the CDC, some people may take longer; or
  • You didn't develop levels of antibodies high enough to be detected by tests -- which preliminary research suggests may happen in mild and asymptomatic cases (Long, Nature Med 2020).

There is currently not enough data to know if a negative result could result from taking the test too late. More research is needed to determine how long significant levels of antibodies to SARS-CoV-2 persist.

The CDC cautions, "Regardless of whether you test positive or negative, the results do not confirm whether or not you are able to spread the virus that causes COVID-19. Until we know more, continue to take steps to protect yourself and others."

This article will be updated as new information is obtained.

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August 9, 2020

personally, i would not trust what the company says about their tests, given the ginning up of cases.

August 1, 2020

The InBios website shows that sensitivity and specificity are 97.8% and 98.9%, respectively, whereas you have it listed as 100% for both. Has there been an update I'm unaware of?

Thank you for providing this excellent information!
August 10, 2020

You are correct that the information provided by the company, based on it own tests, show it to be somewhat less accurate than the results from independent testing by the U.S. government, which are the results we show in the the article above.

July 29, 2020

Is it true that Covid 19 anti body tests can come back positive if one has had a recent common cold?
July 30, 2020

It’s possible that a COVID-19 antibody test with low specificity may detect or show positive results for other viruses that can cause respiratory infections (including colds), such as other coronaviruses. However, this should not occur with COVID-19 antibody tests shown to have 100% specificity. See our table for the best antibody tests, i.e., those with 100% specificity and sensitivity.

July 15, 2020

Do any of the more accurate antibody tests provide the consumer with a specific number related to antibody levels? Or all they all positive/negative/inconclusive?
July 17, 2020

We've added information about this; see "Types of COVID-19 Tests -- Antibody test" in the answer above.

July 12, 2020

Is this statement from above accurate?

Note that in a population where few people (e.g., 5%) actually have antibodies, a test that is not at 100% on specificity, such as the test from Healgen that provides 97.56% specificity and 100% sensitivity, a positive result may only be correct 67.8% the time, although a negative result would nearly always be correct.

If specificity is 97.56% why only correct 67.8% of the time?
July 14, 2020

A good way to understand this is to imagine, for example, a population in which no one is infected. If a test is less than 100% specific, it will sometimes show a positive result when a person is negative. Consequently, a positive result would actually be wrong 100% of the time. So, you can see how, with a test with 97.56% specificity, positive results would be wrong 67.8% of the time in a population where few people have the virus.

July 12, 2020

Can you talk about test results coming back "inconclusive" for Covid?
July 14, 2020

Although the U.S. CDC does not post guidance regarding inconclusive results, the National Health Service in the UK explains the following: "An unclear, void, borderline or inconclusive result means it's not possible to say if you had coronavirus when the test was done. Get another coronavirus test as soon as possible if this happens. If you had a test because you had symptoms, you must keep self-isolating and have another test within 5 days of your symptoms starting." (

July 12, 2020

My daughter and her husband both were sick with covid-19 and now, two month later both tested positive for covid anti-body. However, among their small children who did not have any symptoms, only one out of three tested has anti-body. Which seems to confirm that asymptomatic people don't develop AB.
July 14, 2020

There several reasons why someone may get a negative result with a COVID-19 antibody test. Please see "What Does a Negative Antibody Test Mean?" in the answer above.

July 8, 2020

Would you please offer information on the differences found in the saliva tests versus the blood testing?
August 17, 2020

Please see the information about saliva tests in the "Finding the Best COVID-19 Test -- Virus Test" section in the answer above.

July 8, 2020

Co-Diagnostics company in Utah has a 100% sensitivity and specificity test for Covid-19.
July 8, 2020

The FDA lists their virus test (not an antibody test) as authorized and, according the data submitted by the company to the FDA, it does appear to be highly sensitive and specific.

July 8, 2020

Hi, do you know if people that have the antibody (have been infected), have been re-infected again with the virus?
July 13, 2020

According to the CDC: "We do not know the degree to which previous COVID-19 illness protects against a subsequent SARS-CoV-2 infection or for how long persons are protected. Currently, serologic testing cannot be used to determine if this person may be reinfected. A positive serologic test may be evidence of the prior infection, but it remains unknown to what degree persons with detectable anti-SARS-CoV-2 antibodies are immune to reinfection." (See

June 14, 2020

Which tests are being used by Verily (Project Baseline )? I’m curious to their quality compared to some of the other tests you mention.
June 15, 2020

Project Baseline, run by Verily, is a system for setting up sample collections and getting results to patients. Likely some population data analysis as well. Each site may use a different lab and virus test -- all appear to be PCR based, i.e., looking for the genetic material of the virus. The project is focused on testing people for the virus, not antibodies. Hope that helps. For more information, see this page:

June 11, 2020

Isn't Covid-19 too new of a disease that it is unknown that even if you have the presence of antibodies to the virus it does not indicate immunity?
June 11, 2020

It's still an open question, but the antibodies likely indicate some level of immunity. Not the kind of thing that can be ethically tested in a clinical study on people, so we need to wait for enough population-based data over time to know for sure.

June 10, 2020

You are doing a wonderful job in covering various important aspects of this corona virus epidemic, including evaluating protective gear, testing, benefits of supplements. This is information people really want to know, and you assemble this in a very helpful way. I am grateful for your extended coverage from supplements to other aspects of protecting our health and increasing our knowledge of what is available.
June 10, 2020

Thank you for letting us know!

August 18, 2020


December 23, 2020

More thank you’s from here.

June 10, 2020

This page should be available to the public as a public service, not just to those of us who subscribe to CL. If it were, I would post a link to it on Facebook etc. -- which would be advertising for CL. Please consider this.
June 13, 2020

A free version of this page is available to non-members, but additional information (regarding identification of the most accurate antibody tests and where to get them) does require CL membership. Membership funds our ongoing work.

June 10, 2020

Mayo Clinic says they’ve developed their own approved tests and I know specimens are being sent there from other states. Are those tests in this table?
June 13, 2020

Please see our response on June 3 to a similar question in this section.

June 10, 2020

Greetings! What a remarkably clear, concise and helpful article - very impressive! I have been looking for this kind of summary with no luck until now. Thank you!
June 10, 2020

Thank you for your kind words. We're glad you're finding it helpful.

June 1, 2020

I had tried in past to understand these concepts, but it was murky. I finally watched this video and understood this important info about the accuracy and usefulness of the new antibody tests. this is first explanation of the issue (and math) and what it means that is so clear that I could understand it.

"There is new information from the CDC that COVID 19 antibody testing in populations with a low prevalence of infection results in a high number of false positives (even if the test has a specificity of 95%). Dr. Seheult illustrates why the positive predictive value (and negative predictive value) are generally more helpful than sensitivity and specificity alone (This video was recorded on May 28, 2020) "

Coronavirus Pandemic Update 76: Antibody Testing False Positives in COVID-19 - YouTube
June 4, 2020

Keep in mind that the real probability of a test result being correct for an individual is best determined by the particular circumstances of that individual, as well as the sensitivity and specificity of the test used. For example, has the person exhibited signs of the disease or not, or have they been in high-risk situations or not. The positive and negative predictive values are based on disease prevalance in the population, which won't necessarily reflect the circumstances of the individual. A general discussion about this is found on Wikipedia at

June 1, 2020

Which antibody test is being used in Minnesota by Mayo Clinic? I thought it was a serum test that Mayo developed themselves, but I do not recognize a Mayo test in your list. thanks for tracking this info. I had searched online and found this info on sensitivity and specificity impossible to locate for each test.
June 3, 2020

Mayo Clinic seems to be using an antibody test (for IgG) from Epitope Diagnostics, Inc, according to this page: Currently, this test has not been evaluated by the FDA but is allowed, as it has been filed with the FDA -- you can find it on the list we discuss above. It seems to have been tested by researchers in Germany who found it to have 100% sensitivity (so no false negatives) although only 88.7% specificity (so some false positives) -- see the study at So, if you have antibodies to the virus, it will detect them. However, there's a small chance that a positive result is incorrect.

May 31, 2020

Thanks for synthesizing this information in one place! When we say a test is for example 95% sensitive we mean that of 100 people *known for certain to have a disease*, the test correctly identifies 95 of them (95% true positives). Saying this implies there's a test or situation that is by definition always correct (a gold standard to which other tests are compared). What's the gold standard for COVID-19 antibody testing? For example, might we find 100 people who had positive PCR tests (and a consistent clinical picture), then do antibody tests on them 3 or 4 weeks later? If 95 of them had a positive antibody test, would we say that particular antibody test was 95% sensitive? (And would specificity be established in the same way - find 100 people with consistent negative PCRs and no symptoms, and then some weeks later if 5 of them had antibodies would we say the test was 95% specific?). I asked an epidemiologist this question and they agreed it could be done this way but they weren't sure that was how labs actually got their sensitivity and specificity figures. Thank you!
June 4, 2020

The best explanation of how sensitivity and specificity are being measured with COVID-19 antibody tests is that provided by the FDA on the page we linked to above (full version): "The performance of these tests is described by their "sensitivity," or their ability to identify those with antibodies to SARS-CoV-2 (true positive rate), and their "specificity," or their ability to identify those without antibodies to SARS-CoV-2 (true negative rate). A test's sensitivity can be estimated by determining whether or not it is able to detect antibodies in blood samples from patients who have been confirmed to have COVID-19 with a nucleic acid amplification test, or NAAT. In some validation studies of these tests, like the one FDA is conducting in partnership with NIH, CDC, and BARDA, the samples used, in addition to coming from patients confirmed to have COVID-19 by a NAAT, may also be confirmed to have antibodies present using other serology tests. A test's specificity can be estimated by testing large numbers of samples collected and frozen before SARS-CoV-2 is known to have circulated to demonstrate that the test does not produce positive results in response to the presence of other causes of a respiratory infection, such as other coronaviruses."

william 20046
May 27, 2020

Excellent description of testing issues!

Folks mostly do not understand prevalence, sensitivity, specificity, and sero-conversion.

bill g, mph
May 27, 2020

Thanks. We're staying on top of this area, continually updating.

May 18, 2020

I've seen no mention anywhere of whether biotin supplementation will interfere with some of the antibody tests. I assume it's possible since Troponin, thyroid hormones, Hep A, B, and C antibody tests can be falsely negative if a patient is consuming biotin.
May 21, 2020

Large doses of biotin may interfere with COVID-19 antibody tests. We've added a note about this in the answer above. For information about biotin interference with other types of tests, see the Biotin section of the B Vitamin Supplements Review

May 14, 2020

Hoping there will be a review of the Quest antibody test.
May 14, 2020

As noted above, QuestDirect has stated that it is using the Abbott Architect and EUROIMMUN systems. The results for each are shown above in the "Finding the Best COVID-19 Test" section.

May 13, 2020

This is very interesting: the base rate fallacy, I admit I had never heard of it, but then I avoid statistics if I can. Does this mean even a antibody test 100% both sensitive and specific will have false positives?

"Just Because You Test Positive for Antibodies Doesn’t Mean You Have Them"

In a population whose infection rate is 5 percent, a test that is 90 percent accurate could deliver a false positive nearly 70 percent of the time.
May 14, 2020

A test that is 100% sensitive and specific should not create false negatives or false positives (if done correctly), regardless of the prevalence of disease in the community. But it is true that when the prevalence of a disease is low (i.e., few people have it), a test that not 100% specific could falsely identify more people as positive who are actually negative than who are actually positive.

May 13, 2020

Although this may not be your area of expertise, I'm looking for reasons why and why not to get a voluntary test. I'd like to know if I've been exposed, but if I was then what could happen to me? What could I be forced to do?

There is a story that anybody positive for COVID cannot join the military. I recall a reluctance in the population to be tested for HIV many years ago.
May 21, 2020

These are good questions with both medical and ethical implications and beyond the scope of this article. However, regarding your question about preclusion from military service, this appears to only be true if one has been hospitalized with COVID-19, not just for having tested positive for the virus or antibodies, as noted an article in Stars and Stripes on May 8:

May 13, 2020

You mentioned that some anti-body tests were approved by EU. Which ones? Are they available for purchase in U.S. for home use?
May 21, 2020

We have added a link to a list of tests that conform to the European standards and have the CE mark. Those tests may or may not be available in the U.S., although some have received both FDA allowance and the CE mark. See the full section, Finding the Best COVID-19 Test.

May 13, 2020

I had the virus for 5 weeks, even though I had 3 negative tests. I took my first test at the 2 1/2 week mark, nasal rapid test swab and it was negative. I continued to have symptoms and then 1 1/2 weeks later I took a 2nd swab test that got sent to the lab, negative again. At the 5 week mark, I got a blood test with Quest and it came back negative that I never had the virus or antibodies.

I know I had the virus as the symptoms were it to a T. How can we rely on any of these tests?

May 27, 2020

All of the usual viruses (influenza, etc) are still out there. According to one source, around 50% of the people who were absolutely SURE they had had COVID-19, did not have any antibodies. A PCR test for Covid-19 would not diagnose other viral infections.

May 27, 2020

I had a similar experience. I then realized that I take a lot of supplements including Vit B Complex and other supplements which contain biotin which CAN cause the COVID tests and antibody test to not work correctly. Do you take supplements for nails and hair or others that may contain high levels of biotin?

June 10, 2020

I was actually taking a biotin supplement, which I stopped recently.

July 8, 2020

According to a recent article on CBC.CA, the tests used in Canada (PCR) are at BEST 80% accurate. That's a false negative one out of five times. And that's at the height of symptoms (somewhere around day 7 ). Accuracy decreases thereafter to something like 40% or even less.

May 13, 2020

Is it possible to get the virus sickness twice?
May 13, 2020

A big question, but there is no definitive answer as of yet.

May 17, 2020

Hi: Looks like you can get reinfected according to this NPR article about sailors. "The U.S. Navy says 13 sailors from the USS Theodore Roosevelt who had apparently recovered from the coronavirus and had received negative test results have now tested positive for a second time.

In a statement released earlier on Saturday when five sailors were found to have retested positive, the Navy said the sailors had "met rigorous recovery criteria, exceeding CDC guidelines," including testing negative for the virus at least twice, but have now retested positive. The statement said the sailors had been monitoring their health and adhered to social-distancing protocols while on board the Roosevelt, which has been docked in Guam following an outbreak infecting hundreds of crew members.

"These five Sailors developed influenza-like illness symptoms and did the right thing reporting to medical for evaluation," the statement said.

The Navy has since confirmed to NPR that an additional eight sailors have retested positive for coronavirus, bringing the total to 13."

May 11, 2020

I read your article about covid tests. I know someone who had symptoms and had 2 negative tests. She had trouble breathing and went to the hospital on Sat. Had a negative test and they sent her home. She went back to the hospital Sunday and died there.

Someone my daughter knows had a negative test and then tested positive and died. Makes me worry that these tests aren’t accurate. What do you think?
May 11, 2020

Very sorry to hear that. It could have been the type of tests used, the timing of them (too early or too late), or, as you note, the accuracy of the specific tests.

June 29, 2020

My Abbott antibody test was negative. Was it too late to take the test? It has been 3 months since I had very minor but untested symptoms. My Doctor said almost all the tests are coming in negative. What is going on??
July 7, 2020

We've added information about this in the section "What Does a Negative Antibody Test Mean?" in the answer above.

May 10, 2020

I would like to see your comments as to whether the antibodies actually offer protection from reinfection or not. Many are reporting/speculating that with rapid mutation and reported reinfections that we still are not sure about protection .
May 11, 2020

We, like you, also await definitive evidence on this question.

July 29, 2020

Can you find information for us about T-cell immunity? How to get tested for it? Who is doing good research about it?
July 29, 2020

Information about T-cell immunity in COVID-19 is already found in our answer above, but there are currently no commercially available tests. Should one become available and be authorized for use by the FDA, we will add information about it.

May 10, 2020

Which antibody tests have received approval vs. EUA? There is a list for EUA companies but I have not found the list for approvals.
May 21, 2020

At this time, the FDA has not approved or authorized tests for COVID-19 virus or antibodies, it has only issued Emergency Use Authorizations (EUA) for such tests.

May 10, 2020

I've heard that the nasal swab is very painful. Is the saliva swab just as good?
May 11, 2020

A nasopharyngeal swab, in which a long swab is inserted far back through your nose, can be very uncomfortable. A nasal swab would not go far back and would cause little discomfort. Research is showing saliva to provide a sample that may be just as useful, although most tests at this time are based on nasopharyngeal or nasal samples.

May 11, 2020

A nasal swab should not be painful when using proper technique. One generally needs a tissue and may sneeze and/or laugh from the experience.

November 23, 2020

Given the low accuracy of the Abbott ID Now test, would you not recommend anyone use this test, if offered?
November 23, 2020

As discussed above, it seems to be somewhat less sensitive than other authorized PCR-based tests, i.e., it is more likely to yield a false negative result. If a person is showing symptoms and other test options are not available, it may be worth using, but, otherwise, it would seem better to use a more sensitive test.

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