Flow-through test: Difference between revisions

Revision as of 15:43, 10 March 2016

Revision as of 15:45, 10 March 2016

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In the mid to late 1990’s, a significant number of manufactures switched to newly developed lateral flow tests. However that switch did cause problems as the technology was owned by a company who took an aggressive stance to protect its IP, and have done so successfully. Other companies who did not make the switch further developed flow-through. Some of those companies such as Bio-Rad continued to use original version of the technology that dated back to the late 1980s. Other companies have evolved the technology to varying degrees.

The evolved flow-through tests have benefits that rival or exceed lateral flow technology: they can be transported and stored at room temperature for prolonged periods time and allow rapid diagnostic of multiple diseases on-site with results within minutes.<ref name="medmira_c">http://medmira.com/products/multiplo</ref> This makes them the preferred method in e.g. large screening campaigns but also in situations of accidental blood contact or during labour when immediate treatment of a child exposed to HIV during birth by a HIV- positive mother can significantly reduce mother-to-child transmission.<ref name="rapid-diagnostics">www.medmira.com/products/technology</ref>

== Principle of flow-through tests ==

Flow-through assays are by principle binding-assays. In practice they are mostly applied to detect the interaction of an [[antibody]],from e.g. the test-subjects blood-sample, with immobilized[[Antigen]]s resulting in the formation of an antigen-antibody complex. However, other types of capture-assays are technically feasible; this also includes small molecule capture-assays or antigen tests.<ref name="medmira_d">http://medmira.com/products/technology</ref>

“The test-principle involves a flow of fluid containing the analyte through a porous membrane and into an absorbent pad. A second layer, or submembrane, inhibits the immediate backflow of fluids, which can obscure results. The analyte is captured on the surface of the membrane by analyte capture molecules and then visualized by the addition of analyte detection molecules. These tests can be used to detect both antibodies and antigens. To perform the test, a sample is applied to the membrane and allowed to wick through by capillary action.”.<ref name="rapid-diagnostics">http: //www.rapid-diagnostics.org/tech-flow.htm</ref><ref name="youtube">

http://www.youtube.com/watch?v=0-er3VCk1Cw</ref>

The principle is comparable to lateral flow diagnostic tests, however offers significant technical advantages. Flow-through tests are the assay of choice for point-of-care applications where besides accuracy, speed and testing for several analytes at once are beneficial.