Filtration products serve a critical function in diagnostic and clinical testing. Their primary function is to isolate cells from an analyte for further study or experimentation. While many of these tests originated in a laboratory environment, they are commonly used in homes worldwide.

In a laboratory, scientists conduct an assay to determine the presence, amount, or functional activity in an analyte. For biochemical assays, the intended goal may be to understand the efficacy of a drug or the presence of specific cells or proteins in the analyte.

A lateral flow test begins with placing the analyte on the sample pad at one end of a filtration membrane. Capillary flow occurs as the analyte moves laterally through the membrane. A conjugate pad absorbs the analyte and uses reagents to activate and optimize the target molecule. Once optimized, this molecule seeks out its chemical partner (e.g., an antigen will seek an antibody) and attaches itself, forming a bonded pair. This pair of molecules then collect on a test line and control line. How well the molecules attach to the antibodies in the test and control line determines the test results.

While scientific tests can be very complex, their real-world application is very familiar to many people across the globe. Lateral flow tests are used in home pregnancy tests to detect a specific hormone released during pregnancy. Additionally, many home COVID-19 tests use a similar method to identify the presence of the COVID-19 virus. The filtration medium is the key component that makes each test kit effective.

Specific filtration mediums used in lateral flow testing include nitrocellulose, glass fiber, and polyethylene. Nitrocellulose membranes display excellent protein binding properties and provide clear results, making them suitable for various assays. Glass fiber can facilitate faster flow rates when a rapid result is critical, such as in acute testing scenarios. Glass fiber is also used frequently as a pre-filter to remove large particles from an analyte before sensitive screening processes. Polyethylene membranes are another option, primarily employed for their robustness and compatibility with many reagents, making them versatile for different applications. Each of these materials plays a crucial role in ensuring the precision and efficiency of the test by optimizing the interaction between the analyte and the reagents.

As technology advances, innovative filtration mediums will continue to enhance the reliability and accessibility of testing, empowering individuals and healthcare professionals alike to make informed decisions based on accurate results.