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Lateral flow tests also known as lateral flow immunochromatographic assays, are simple devices intended to detect the presence (or absence) of a target biochemical marker without the need for specialized and costly equipment. The most common of these devices is the home pregnancy test which tests for hcG in urine. Outside of pregnancy testing, these simple tests can be used with blood, urine or saliva as a quick diagnostic for the presence of drugs, diseases like HIV, Hepatitis C or Malaria as well as more common items like the presence of Vitamin B12.
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Each test strip is often made from materials that enable capillary action, such as porous paper or polymers, to allow the test fluid to ‘flow’ along the strip. Once soaked, the fluid migrates to the second element (conjugate pad) in which the manufacturer has stored the so-called conjugate, a dried format of bio-active particles contains everything to guarantee an optimized chemical reaction between the target molecule (e.g., an antigen) and its chemical partner (e.g., antibody) that has been immobilized on the particle's surface. A combination of the chemical reaction and capillary action dissolves those bio-active particles and transports them to the third area where the manufacturer has immobilized a third particle which will capture the target molecules and make the strips change color as the target molecules ‘arrive’. As well as the test line, which becomes visible in the presence of the target substance, there is often a control line to ensure that the ‘strip’ is working properly.
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Each of these test strips would normally require a human eye to adjudicate the presence of the target substance, however weak presence of the substance may show a weak or inconclusive result. Alternatively, the strip manufacturer may want the test line only to be visible under ultraviolet light so that those being tested cannot know the results.

Dr Neven Karlovac explained to us how Cellmic LLC, a young technology company dedicated to improving patient healthcare with the use of smartphones and biophotonics by licensing the work of Professor Aydogan Ozcan and his research group at UCLA to commercialize a suite of rapid diagnostic test readers for advancing diagnostic accuracy and access. The biophotonic devices use the markers in the test strips with the photonics found in cellphone cameras to develop readers that can read both chromatographic and fluorescent rapid tests to reduce user error. Each reader is based on an Android smartphone, paired with a ‘case’ that includes LED’s to increase the light available, the portable readers automatically carries out the processing of the test strips, using the cellphone camera, something that previously required a desktop reader. The profile for each test type can be loaded onto the smartphone so the same devices can be used for multiple test types. The whole process can be seen in this video


Dr Karlovac explained how the Android devices (free with every reader), have many default services removed to improve security and reduce violations of the HIPAA act in the United states and equivalent medical privacy acts in other countries around the world. One of the services not disabled is the GPS location, as combined with cloud services helps in the use of the readers in two ways. Firstly, each test result can be geo-tagged so if an organization carrying out tests in the field needs to generate a map of test results they can do so by uploading the results onto a secure server, and secondly not all tests can be used in every country so cloud services can be used to ensure tests can be run only in countries where they are properly licensed for use.

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As new test strips are developed, the test strip manufacturers can create profiles for each of their tests so the image sensor knows what is should be looking for and what density of particles is considered a positive (or negative result). These profiles can then be uploaded to a secure server to be downloaded by any user of the device.

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In addition to the mobile assay readers, Cellmic also offers a standalone microscope that again when paired with a cellphone camera can provide sub-cellular resolution over a field of view of that is an order of magnitude larger than the imaging area of a typical 10X objective lens, allowing more ‘items of interest’ to be found compared to traditional techniques.


The talk really enabled those of us who attended to understand how something a simple as a cellphone camera, combined with cloud services can make traditional assay reading a much more powerful medical diagnostic tool.