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COVID-19 Ag Self Test – CE Marked

CTK’s OnSite COVID-19 Ag Self Test aims to restore a sense of normalcy to everyday life through reliable COVID-19 rapid testing in the safety and convenience of your home.


CTK’s OnSite COVID-19 Ag Self Test is the same test used by frontline workers in various Point-of-Care and resource-limited settings but now tailored for your use!

An easy-to-use test that screens for COVID-19 in 15 to 20 minutes in the comfort of your home.

  • Uses nasal swab for ease of use and minimizing discomfort
  • Conveniently dispose of kit components through the provided waste bag

    How the OnSite COVID-19 Ag Self Test Works

    Test in 4 Simple Steps

    Be sure to read the full instructions provided in the kit and review this procedure video below

    Additional Resources


    • Check the expiration date of the test before using it.
    • Use a flat, well-lit surface to perform your test.
    • Clean your test surface before opening the test kit.
    • Blow your nose before testing.
    • Wash your hands with soap and water before starting.
    • Read the instructions before testing and follow the steps in order.
    •  Swab both nostrils.


    • Begin the test unless you have at least 25 minutes to complete all of the steps correctly; if this is your first test, allow for extra time.
    •  Use the kit if the sealed packaging is damaged.
    • Touch the fabric tip of the swab with your hands.
    • Insert the swab any deeper if you feel resistance or pain.
    • Move the cassette after adding the 3 drops of extracted sample.
    • Reuse any components from the first test.

    If you have a question about your test and would like to request support from our Technical Support team, please fill out the form below. To help us process your information quickly and effectively, please provide as much information as possible. If you would like to speak to one of our Technical Support team members, please call +1-833-919-0617.

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        1. Does this test hurt?

        No. The nasal swab has a fabric tip and should not hurt. Sometimes the swab can tickle or cause slight discomfort. If you feel pain, stop the test and seek advice from your healthcare provider.

        1. Are there risks in taking this test?

        Potential risks include:

        • Possible discomfort while collecting the nasal sample
        • Possible incorrect results (refer to “Read the result” on the IFU)

        Potential benefits include:

        • Your results may limit the spread of COVID-19 to your family and others in the community.
        • The results, along with other information, can help your healthcare provider make informed recommendations about your care.
        1. I tested negative, does that mean I don’t have COVID-19?

        A negative test result means that antigens from the virus that causes COVID-19 were not found in your sample.

        You might have a different virus or infection causing your symptoms.

        If you continue to have symptoms associated with COVID-19 such as fever, difficulty breathing and/or cough, you should take another test.

        A negative test result does not guarantee that you don’t have coronavirus. You may have COVID-19 and still get a negative result (known as a false negative) if:

        • You did not perform the test accurately, such as not collecting the sample correctly or not waiting 15 minutes for your result.
        • The amount of virus antigen present in the sample was below the test limits.
        • You have had signs and symptoms of COVID-19 for longer than seven (7) days. This means you can still have COVID-19 even though the test is negative. Please see your healthcare provider for the next steps you should take.
        1. What should I do if I test positive?

        A positive result means you are very likely infected with coronavirus and there is a risk of infecting others. Follow the recommended guidelines from your health authorities such as self-quarantining at home to avoid spreading COVID-19 to others. Follow up with your healthcare provider to determine the best care for you based on your results. You may need additional testing depending on your personal history.

        1. Why do I need to blow my nose before the test?

        Too much viscous mucus on the swab if transferred to the test cassette, might give incorrect results. It is important you blow your nose before collecting the swab sample.

        1. What is the difference between this antigen self-test and a molecular test?

        The OnSite COVID-19 Ag Self Test detects a viral protein in 15 minutes. Molecular tests, such as PCR tests, detect genetic material from the virus. Antigen tests are faster and highly specific for detecting the virus, but not as sensitive as molecular tests. A positive result for an antigen test is highly accurate, but a negative result does not rule out infection, in particularly if your symptoms last longer than 7 days.  If your test is negative but your symptoms persist, you should discuss with your healthcare provider if additional testing is necessary or if you should continue isolating at home.

        1. How accurate is the OnSite COVID-19 Self Test?

        The OnSite COVID-19 Ag Self Test kit is 98.6% accurate when tested by laymen. No test is 100% accurate.

        1. Is the liquid in the buffer tube harmful?

        The chemicals in the buffer tube (a detergent, ProClin 300, and sodium azide) are known to be non-toxic, at the levels present in the liquid. The buffer should only be used as directed; do not ingest; keep out of the reach of children; avoid contact with skin and eyes. If the liquid contacts the skin or eye, wash with water. If irritation persists, seek medical advice: https://www.poison.org/contact-us or 1-800-222-1222   

        1. Why does my test not have a C line?

        No C line means your result is invalid and there was a testing error. This could be caused by overflowing the test cassette with too much sample, or by extra mucus on the sample. You need to read the procedure instructions and repeat the entire procedure with a new kit.

        1. Can I get a false positive result?

        Yes, false positive results are possible. The OnSite COVID-19 Ag Self Test kit was shown to be 100% specific in a clinical study in symptomatic patients, with no false positive results observed. However, while a positive result means that you are very likely infected with coronavirus and could infect others, false positive results can be obtained, as no test is 100% accurate.

        1. What if a test line appears after 20 minutes?

        It is an invalid result. You must read results within the 15–20-minute window. Any result read later than 20 minutes must be repeated with a new test.

        1. What does it mean if the Ag line is very light?

        As long as the C line appears, any visible Ag line is a positive result. If you are not confident in the result interpretation, repeat the test.

        1. Can I take a throat or saliva sample instead of a nasal sample?

        No. This test is specific for testing nasal swab samples ONLY. Using a throat or saliva sample will give inaccurate results.

        1. I had symptoms for more than seven days. Can I still use this test?

        No. If you had symptoms for more than seven days you can still have COVID-19 even though the test is negative. Please see your healthcare provider for next steps.

        1. What if I opened the pouch too early?

        Carefully read the Instructions for Use and follow the procedure stated in the Quick Reference Guide. If the steps are not followed as instructed, the performance of the test may be affected. Opening the pouch too early and exposing the cassette prematurely may lead to inaccurate results.

        1. What if I spilled the contents of the buffer tube while performing the test?

        Clean the spill with dish soap and water. Dispose all contents of the open test kit into the waste bag, then discard the waste bag in the trash can. Repeat the entire procedure with a new test.

        1. Can I test a child under 12 with this test?

        Children under 12 years of age should be assisted by an adult.

        1. Can this test detect all the COVID-19 variants?

        The OnSite COVID-19 Ag Self Test detects the California, Nigeria, and India/Delta variants. For the most up-to-date information on what COVID-19 variants this test can detect, refer to the CTK website: https://www.ctkbiotech.com

        CTK was founded in 1998 by scientists who teamed up to design infectious disease test kits that meet demand while for every market. In these nearly 25 years of developing and producing test kits, improving global health has been at the heart of CTK’s innovations.

        CTK’s OnSite brand, trusted by pathologists and medical technologists worldwide now brings you the OnSite COVID-19 Ag Self Test, designed for non-professional use, bringing the quality of the lab to the convenience of your home, office, any location where a test result is required.