COVID-19 & Lateral Flow

Novel coronavirus (COVID-19), first reported in December 2019, caused an outbreak in Wuhan, China. It soon spread to other parts of the world. The ongoing global pandemic poses a challenge, as infection is now widespread internationally.

As of time of publication, over 55 million cases have been diagnosed globally with more than 1.3 million fatalities.

COVID-19 belongs to a family of viruses, with some causing less severe diseases, for example the common cold, some others causing much more severe diseases such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS).

COVID-19 presents with a range of symptoms of varying severity. Asymptomatic infection also occurs often (estimated >50% cases).

Most common COVID-19 symptoms are fever, a new and continuous cough, shortness of breath, fatigue, loss of appetite, loss of smell and or taste. Non-specific symptoms include fatigue, headache, nasal congestion, diarrhoea, nausea, and vomiting. Atypical symptoms can present be older and immunocompromised people such as delirium and reduced mobility.

Transmission of the virus occurs through infected respiratory droplets in the form of sneezing, coughing, or speaking which are released into the air. They can come into contact with a person, who may inhale or have the pathogen on their skin or touch an object, such as surfaces, that have been infected then they go on to touch their face or mouth and contract the infection that way.

Immune system and antibody production

There are three lines of natural defence that the body has to help protect the body from infection.

The first and second line of defence are non-specific.

The third line of defence against microbial infection is the human immune system. The immune response, identifies the surface of a foreign microbe invading the body and this is referred to as an antigen.  The immune system sees this as a threat and stimulates an immune response. On the surface of pathogens there are proteins which are known as antigens, which are unique to that pathogen. When these pathogens invade the body, a type of white blood cell, a lymphocyte, identifies the antigen as foreign, and creates an antibody, specific to that antigen. The antibody then destroys the antigen (pathogen). After recovering from an infection or receiving a vaccine, the body produces memory cells, again, specific to that antigen, to help the body to remember that infection and to recognise which antibodies it needs to produce, if the body is infected again.

Principle of COVID-19 Antigen Rapid Cassette Lateral Flow Test

The Healgen COVID-19 rapid antigen test is an immunochromatographic membrane that uses sensitive monoclonal antibodies to detect protein from SARS-CoV-2 in both nasopharyngeal (nose) and throat swab. The test strip is fixed inside a plastic device containing various parts, sample pad, reagent pad, reaction membrane and absorbing pad. The reagent pad is conjugated with the monoclonal antibodies against the protein of SARS-CoV-2. Once the sample is collected and added into the sample well, conjugates dried in the reagent pad are dissolved and migrate along with the sample. If SARS-Cov-2 antigen presents in the sample, a complex formed between the antibodies coated in the test line region.