Cellex qSARS-CoV-2 Neutralization Antibody Rapid Test

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Technical Manual Data Sheet Brochure

Cellex SARS-CoV-2 Neutralization Antibody Rapid Test

Intended Use

The Cellex SARS-CoV-2 NAB Rapid Test is a lateral flow immunoassay intended for the qualitative detection of neutralizing antibodies to SARS-CoV-2 in serum, plasma and whole blood. The Cellex qSARS-CoV-2 NAB Rapid Test is intended for use as an aid in identifying individuals with an adaptive immune response to SARS-CoV-2, indicating recent or prior infection. The Cellex qSARS-CoV-2 NAB Rapid Test should not be used to diagnose acute SARS-CoV-2 infection. For prescription use only. For in vitro diagnostic use only. For emergency use authorization use only.

Test Summary and Explanation

Coronaviruses (CoV) are a large family of viruses that cause illness ranging from the common cold to more severe diseases such as Severe Acute Respiratory Syndrome (SARS-CoV). SARSCoV-2 is a new strain that has not been previously identified in humans. Coronaviruses are zoonotic, meaning they are transmitted between animals and people. Several known coronaviruses are circulating in animals that have not yet infected humans.

SARS-CoV-2 is a new coronavirus, causes an infectious disease named COVID-19 (Coronavirus disease 2019). Patients with SARS-CoV-2 report a mild to severe respiratory illness with symptoms of: fever, cough, shortness of breath. There is an urgent need for rapid tests to manage the ongoing pandemic.

SARS-CoV-2 has several structural proteins including spike (S), envelope (E), membrane (M) and nucleocapsid (N). The spike protein (S) contains a receptor-binding domain (RBD), which is responsible for recognizing the cell surface receptor, angiotensin converting enzyme-2 (ACE2). It is found that the RBD of the SARS-CoV-2 S protein strongly interacts with the human ACE2 receptor leading to endocytosis into the host cells of the deep lung and viral replication.

Infection with SARS-CoV-2 initiates an immune response, which includes the production of antibodies in the blood. Not all antibodies can block cellular infiltration and replication of the SARS-CoV-2 virus. The subpopulation of the antibodies that can block cellular infiltration and replication of the virus are named neutralizing antibodies. It is unknown how long it takes for neutralizing antibodies to be produced, and if they are always produced after SARS-CoV-2 infection. While individuals infected with SARS- CoV-2 develop antibodies to the virus, not all of them develop neutralizing antibodies to SARS-CoV-2.

The Cellex qSARS-CoV-2 NAB Rapid Test is intended for qualitative detection of neutralizing antibodies indicative of SARS-CoV-2 infection and is to be used as a predictor of immunity condition of COVID-19.

Test Principle

The Cellex SARS-CoV-2 NAB Rapid Test use a recombinant protein representing the RBD of the S antigen in a double-antigen sandwich assay format, which captures predominantly anti-SARS-CoV-2 IgG, but also anti-SARS-CoV-2 IgA and IgM.

The Cellex SARS-CoV-2 NAB Rapid Test has two pre-coated lines, “C” Control line, “T” Test line on the surface of the nitrocellulose membrane. The nitrocellulose membrane is attached onto a plastic backing card and combined with the other reagents and pads to construct a test strip. The test strip is encased inside a plastic device. Both the control line and test line in the result window are not visible before applying any specimens. When the specimen is added into the test device, the specimen is absorbed into the device by capillary action, mixes with the SARS-CoV-2 antigen-dye conjugate and migrates along the membrane strip to the reading window. On the nitrocellulose membrane within the reading window SARSCoV-2 S-RBD antigen is precoated at T area and a goat anti-rabbit antibody is precoated at the C area. If antibodies to SARS-CoV-2 S-RBD present in the specimen, the T line will become visible. If the specimen is SARS-CoV-2 S-RBD antibodies negative, only the C line will become visible.

If the C Line does not develop, the assay is invalid regardless of color development of the T Line. Repeat the assay with a new device.

Reagents and Materials

Reagents and Materials Provided

There are three kit sizes. Their kit component configurations are provided below:

Kit Size (#of Tests) 1 25
Test Cassette (#) 1 25
Sample Diluent (# of Bottles) 1 1
Transfer pipette 1 25
IFU Leaflet 1 1

Material Required But Not Provided

  • Timer

Storage and Stability

  1. Store the detector buffer at 2-30°C.
  2. Store the Cellex SARS-CoV-2 NAB Rapid Test at 2-30°C; It can be stable until the expiration date.
  3. If stored at 2-8°C, ensure that the test device is brought to 15-30°C before opening.
  4. Do not freeze the kit or store the kit over 30°C.

Test Procedure


Step 1: For fresh samples, begin with Step 2. For frozen samples, bring the specimens and test components to room temperature, and mix the specimen well once thawed.

Step 2: When ready to test, open the pouch at the notch and remove the test device. Place the test device on a clean, flat surface.

Step 3: Label the device with specimen ID number.

Step 4: : Using a transfer pipette, transfer serum, plasma or whole blood, careful not to exceed the specimen well. The volume of the specimen is around 40 μL. For better precision, transfer specimen by a pipette capable of delivering 40μL of volume. Holding the transfer pipette vertically, dispense 40µL of the specimen into the center of the sample well (S well) making sure that there are no air bubbles. Then, add 1 drop of Sample Diluent immediately into the sample well (S well).

Step 5: Set up a timer.

Step 6: Read the results in 15-20 minutes. Don’t read results after 20 minutes. To avoid confusion, discard the test device after interpreting the result.


While we believe this kit is to be an effective indicator of infection we cannot guarantee 100% accuracy so the patient should still be advised to follow government guidelines for those exhibiting symptoms and those who aren’t regarding hygiene, self-isolation and other measures even if the test is negative.

  • Negative results do not rule out SARS-CoV-2 infection, particularly in those who have been in contact with the virus. Follow-up testing with a molecular diagnostic should be considered to rule out infection in these individuals.
  • Results from antibody testing should not be used as the sole basis to diagnose or exclude SARS-CoV-2 infection or to inform infection status.
  • Positive results may be due to past or present infection with non-SARS-CoV-2 coronavirus strains, such as coronavirus HKU1, NL63, OC43, or 229E.
  • This kit is for Professional-Use-Only.