How it works

Why reading a Lateral Flow Test is not as easy as you may think

When you conduct a lateral flow test (LFT) you prepare a test sample taken from your nose and throat and add this to a test cassette. This cassette contains chemicals that react with your sample to see if any coronavirus antigen is present. The test will show what are called a Control Line (C line) and a Test Line (T line). The more coronavirus antigen present, the stronger the Test Line appears in the test cassette viewing window. But for low levels of infection, the Test Line may be faint. In fact, it may be difficult to see at all. But even a faint Test Line signifies a positive COVID-19 test.

Test To Go uses sophisticated software to turn your smartphone into a highly accurate LFT reader. So much so, that Test To Go has a visual acuity that is 1.6 to 3 times greater than that of the average person, making it easier for Test To Go to discern a positive test result when the human eye may miss it.

Test To Go app showing submit photo of test screen to get results.

The MagnifEyeTM software

At the heart of the Test To Go app is MagnifEye, which enables your smartphone to accurately determine if an LFT is positive, negative, or void.

MagnifEye is a software application containing is a suite of algorithms hosted within a secure cloud environment that reads and interprets LFTs from images of the test results. The application uses state-of-the-art AI and system architecture and currently has capacity to read 40 million+ tests per week and provide results in under 2 seconds.

In addition to reading and interpreting LFT results, the software can identify tests that may have been scanned previously, or that may have been damaged or altered in use. Thereby reducing the likelihood of fraudulent tests being submitted.

One of the MagnifEye algorithms helps users capture high-quality images of their test results. It will only snap a test cassette image when:

  • The image fills the framing grid
  • is on a plain background
  • is in focus
  • shot directly from above
  • under good lighting conditions

Only when MagnifEye sees these conditions are met will the image be automatically captured for submission by the app. The auto-finder makes user error impossible.

Test To Go app showing test capturing screen.

Test To Go significantly outperforms the human eye in reading lateral flow tests

A study carried out in Cambridge1, United Kingdom, in April 2021 set out to determine the ability of untrained observers to read lateral flow tests dosed with varying concentrations of recombinant N-nucleoprotein from SARS-CoV-2. In addition to untrained observers reading the results, the Test To Go smartphone app was used to read the same results offering a direct comparison between human observation and app technology.

The study was carried out with 305 members of the public. They ranged in age from 20s to 90s with around 90% under the age of 65. If a person normally wore glasses to aid their near vision they were asked to wear them when reading lateral flow tests. The visual acuity of each participant was measured using a Jaeger eye chart. A Jaeger chart uses blocks of successively smaller text. When held at a normal reading distance (40cm) a person is asked to read the smallest text they can reliably see without squinting. With an ability to read the smallest text a person is said to have a Jaeger score of 1 (J1). Of the 305 volunteers, 222 (73%) had a Jaeger score of 1. The remainder varied from J2 to J7 with a trend to reduced visual acuity after the age of 45.

SARS-CoV-2 N protein antigen was diluted from 500 pg/ml, representing a highly infected individual with a high level of antigen present, through decreasing amounts down to 0 pg/ml, or no virus antigen present. Each dilution was applied to Excalibur Rapid SARS-CoV-2 Antigen Test cards and read by participants and by the Test To Go app.

Results:
The Test To Go app consistently read a higher number of positive results compared with untrained participants even at the highest concentration of SARS-CoV-2 N-protein antigen used in this study.

Performance of participants reading Excalibur Rapid SARS-CoV-2 Antigen Test cards dosed with SARS-CoV-2 N‑nucleoprotein in comparison with the Test To Go app.

Reference: 1. Cambridge, UK 23rd and 24th April 2021. For further information click here.