What is COVID-19 & FLU A/B Rapid Antigen Test? - Vitrosens Biotechnology

What is COVID-19 & FLU A/B Rapid Antigen Test?

27 April 2022

What is COVID-19 & FLU A/B Rapid Antigen Test?

What is COVID-19 & FLU AB Rapid Antigen Test

In a nutshell, the COVID-19 & FLU A/B Rapid Antigen Test is an integrated combination test that enables the rapid differential identification of infections caused by any of these respiratory viruses using only a single nasal or nasopharyngeal patient sample. The COVID-19 & FLU A/B Rapid Antigen Test, which is designed for professional use in both laboratory and point-of-care settings, supports the diagnosis of patients with symptoms associated with COVID-19 or influenza during the acute phase of the infection by delivering three results from a single specimen. Thus, it helps the rapid identification and isolation of infectious patients, optimization of patient care, and the expansion of testing capacities. Read more to learn about the test principles, the procedure, and main areas of use for the COVID-19 & FLU A/B Rapid Antigen Test.

How Does the COVID-19 & FLU A/B Rapid Antigen Test Work?

The COVID-19 & FLU A/B Rapid Antigen Test is a lateral flow immunochromatographic membrane assay in sandwich format utilizing the colloidal label for the simultaneous qualitative detection and differentiation of SARS-COV-2, influenza type A, and influenza type B nucleocapsid antigens in human nasal and nasopharyngeal samples. The COVID-19 & FLU A/B Rapid Antigen Test can detect infections with SARS-CoV-2 and influenza A and B within the acute phase, which refers to the first 7 days from the onset of symptoms for infections with SARS-CoV-2, and the first 4 days from the onset of symptoms for infections with influenza. Like other antigen tests, The COVID-19 & FLU A/B Rapid Antigen Test relies on the interaction between antigens antibodies.

After the nasal or nasopharyngeal specimen is transferred from the swab into the buffer solution, a few drops of the processed sample are dispensed into the sample well (S) on the test strip. The test strip contains several lines of highly sensitive anti-SARS-CoV-2, anti-influenza A, and anti-influenza B antibodies to bind and capture antigens specific to each pathogen. If antigens of either of these pathogens are present in a sample, the extracted antigens first bind to colloidal gold-labeled mobile antibodies to form antibody-antigen (Ab-Ag) complexes. Next, these antibody-antigen (Ab-Ag) complexes are captured by a second line of immobilized antibodies in the test region. Thanks to the colloidal gold-labeling, the captured antibody-antigen (Ab-Ag) complexes form a colored line in the test region for that specific pathogen. The presence of the test line (T) indicates an infection with a specific pathogen.

Colloidal gold-labeled antibodies also bind to antibodies in the control region to form a colored line that functions as a procedural control. The presence of the control line (C) indicates the adequacy of sample flow and the validity of the test. If the (C) line is not visible, the test results are considered invalid. The procedure must be repeated with another test kit.

What are the main areas of use for the COVID-19 & FLU A/B Rapid Antigen Test?

The usage areas of COVID-19 & FLU A/B Rapid Antigen Tests can be classified into four categories.

  1. A) For the detection of infectious patients

For highly infectious viruses such as SARS-CoV-2 or Influenza A and B, it may be critical to identify and isolate infected individuals to reduce community spread. The rapid detection and differentiation of SARS-CoV-2 and Flu A/B is vital for the immediate application of the required isolation measures. Timely isolation helps prevent an infectious individual from transmitting the virus to others, break transmission chains, and control epidemics or pandemics.

  1. B) For the rapid diagnosis and differentiation of SARS-CoV-2 and Influenza A/B

Symptoms for SARS-CoV-2 and Influenza A and B are quite similar. Therefore, especially as the flu season intersects with the pandemic, it is critical for healthcare professionals to quickly determine which infection may be present in individuals that display symptoms associated with COVID-19 and influenza.

  1. C) For the optimization of patient treatment pathways

Reliable and rapid diagnostic devices enable healthcare professionals to make timely and well-informed decisions. These test kits help patients to access to treatment options as early as possible when antiviral medication treatments are most effective. Early access to appropriate treatment can reduce both the duration and the severity of the symptoms experienced by people with COVID-19 or influenza infections.

  1. D) For the expansion of testing capacities

Introduction of rapid antigen-based diagnostic devices can help scale up testing capacities and support decentralized testing strategies. Especially in remote, low infrastructure or resource-limited areas, the introduction of the COVID-19 & FLU A/B Rapid Antigen Test and similar rapid antigen tests can significantly improve the access to testing by reducing the need for laboratory technology, equipment, and resources. Point-of-care and self-testing also prevents the overcrowding of testing centers and improves access by allowing us to take the test to the patient.

COVID-19 and Flu: What are the Similarities and Differences?

Influenza and COVID-19 are both infectious viral respiratory illnesses that transmit mainly by particles or droplets containing virus that are released into the air when infected people cough, sneeze, talk and so on. As these infections can have very similar symptoms, it is not possible to differentiate between them by examining symptoms alone. Common symptoms for infections with both viruses include fever, cough, fatigue, sore throat, runny nose, diarrhea, headache, and shortness of breath. While loss of taste or smell may occur in influenza infections, it is more commonly experienced in COVID-19 infections. However, while it takes 1 to 4 days for people infected with influenza viruses to experience symptoms, it may take anywhere from 2 to 14 for those infected with SARS-CoV-2.

Although symptoms and transmission paths of the two viruses are similar, SARS-CoV-2 is known to be more contagious than influenza viruses. Not only SARS-CoV-2 spreads faster and easier, but a person stays infectious for a longer period if they are infected with SARS-COV-2.

Both influenza viruses and SARS-CoV-2 may lead to the development of severe symptoms. Risk groups for the two viruses are similar, however, SARS-CoV-2 might cause more severe illness and complications compared to influenza as hospitalization and death occur even in healthy individuals. Those infected with SARS-CoV-2 may also develop multisystem inflammatory syndrome (MIS) or experience post-COVID-19 conditions that can last for months after their initial infection.

Does Influenza Have Variants?

There are four types of flu viruses: A, B, C and D. Influenza type A and B are commonly responsible for seasonal flu epidemics. Influenza type A viruses are the primary cause of flu epidemics and are the only flu viruses to cause pandemics. Type A and B viruses can be further categorized into sub-variants, lineages, clades, and sub-clades. Although Type C viruses may cause mild respiratory symptoms, it is not known to cause epidemics. Influenza Type D predominantly infect and cause illness in cattle. It is not known to affect humans. Modern vaccines target Influenza type A and B as these viruses constitute the most common causes of flu in humans.


  1. Pormohammad, A., Ghorbani, S., Khatami, A., Razizadeh, M. H., Alborzi, E., Zarei, M., Idrovo, J., & Turner, R. J. (2020). Comparison of influenza type A and B with COVID‐19: A global systematic review and meta‐analysis on clinical, laboratory and radiographic findings. Reviews in Medical Virology, 31(3). https://doi.org/10.1002/rmv.2179
  2. Shen, C., Tan, M., Song, X., Zhang, G., Liang, J., Yu, H., & Wang, C. (2020). Comparative Analysis of Early-Stage Clinical Features Between COVID-19 and Influenza A H1N1 Virus Pneumonia. Frontiers in Public Health, 8. https://doi.org/10.3389/fpubh.2020.00206
  3. Nersesjan, V., Amiri, M., Christensen, H. K., Benros, M. E., & Kondziella, D. (2020). Thirty-Day Mortality and Morbidity in COVID-19 Positive vs. COVID-19 Negative Individuals and vs. Individuals Tested for Influenza A/B: A Population-Based Study. Frontiers in Medicine, 7. https://doi.org/10.3389/fmed.2020.598272




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Copyright by Vitrosens Biotechnology. All rights reserved.