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Comment by shiftpgdn | Hacker News Reader

If you read the full Twitter thread they explain that paper doesn’t work for everyone (the color blind and the incompetent, for example.) There is a use case, it just might not be for you.

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The Abbott test has two lines separated… if two then positive, if one then negative. You don’t even need to tell the colors apart.

You do, however, need color vision to tell that the control line changed from blue to red (which the instructions tell you to do to verify that the test is working correctly)

Every Covid self test I've ever used had two red lines for postive and one red line for negative. Why are there tests out there that need color vision?

That's not true for every test, the one I just used begins with no line and then a line appears. So you don't need color vision. You do still need vision, but it's hard to use a COVID test otherwise.

Sure, but the parent specifically referenced the Abbott test. And the Abbott test instructions tell you to discard and not use the test if the blue line is not present.

See pages 6 and 7: https://www.fda.gov/media/141570/download

Every test I've done (provided for free on the NHS, btw) has just been two red lines.

The control line doesn't show up until the buffer solution has wicked along the test strip, so the verification is "does the line next to the letter C show up?"

Yes, but the parent was writing about the Abbott Labs BinaxNOW test, specifically (which I have also used).

The directions indicate to verify that the blue control line is present prior to adding the swab, and that the test should not be used if the blue line is not present.

You can verify this for yourself by downloading the official instructions here: https://www.fda.gov/media/141570/download

That is something your phone can do for you without the need for a disposable chip

The use case is valid but the solution is completely overkill.

You could do this with an analogue circuit and two LEDs.

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