Ever since the COVID-19 pandemic was identified in December 2019 and then classified as a pandemic in March 2020, our lives as we know it have changed. From increased public-health strategies to a focus on testing and analysis and vaccine development – these terms have made headlines the world over.

One such term is Rapid Testing and with the increasing popularity of the term, the time is ripe to understand the differences among such tests. But first, let’s understand what is implied by the term Rapid Diagnostic Test. Simply put, such tests provide a rapid means of diagnosis and are suitable for preliminary or emergency medical screenings. They are used to test for a particular antibody and are relatively economic in cost.

An example of such a test is the Lateral Flow Test. This is an antibody based test in which an extracted sample (sometimes in solution depending on the test) is applied to the end of a test strip – usually a piece of paper pre-treated with the specific antibody and coloured markers at specific points. The sample solution travels through the testing pad and if the antibody is present, the coloured beads get activated to produce a positive result, usually in a matter of minutes or a few hours.

A home pregnancy test is a common example of the lateral flow test – with the only difference being that the presence of certain hormones is what is being tested for, instead of antibodies. These tests primarily produce yes/no results and are more qualitative than quantitative in nature. There are, of course, plenty of variables and even a few exceptions. Some lateral flow kits require lab equipment and careful temperature controls, while others do not.

Unlike lateral flow tests, Enzyme-Linked ImmunoSorbent Assays, or ELISAs, are more complex. Although the results take longer and the process involves complex steps and laboratory equipment, ELISA’s are important because their highly specific nature allows for more quantitative results.

Herein, antigens in the treated sample are attached to a testing surface and a matching antibody is applied over the surface so it can bind to the antigen. Different solutions are then applied to the surface and then washed off. If the antibody finds what it’s looking for, an enzyme that is linked to it, it will change the colour of the enzyme’s substrate, indicating a positive result. Often, a spectrometer is used to give quantitative values for colour strength.

Different types of ELISA’s include sandwich ELISAs (sandwiching the antibody between two antigens), Polymerase Chain Reaction (making particles in the sample compete with a known antigen for landing spots on the antibody) and PCR or Polymerase Chain Reaction tests which detect the presence of an antigen at the molecular level.

While both these types of tests have their benefits, understanding their cost differences, specificities, advantages and disadvantages can help determine what would be a better choice for your needs.