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Comment by snypher | Hacker News Reader

"improve the clarity of a test by displaying “pregnant” or “not pregnant” on the display instead of the usual lines that can be difficult to read."

I generally agree with your point, but there is an accessibility use case for this test. If you are able to, you should choose the less wasteful option.

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If you can make specific lines appear as a result of a chemical reaction… can’t you make a line or dot appear next to printed “pregnant” “not pregnant” words instead? No microchip required..

Disclosure; I know nothing about this.

To be honest two lines or one lines ???. Where the hell is the package liner ???. I can see the point of having a clear message for a pregnancy test.

Right. and that was part of my point though - if the chemical reaction is able to make one or two lines appear, then it's surely able to make specific areas appear that are clearly labeled pregnant or not pregnant - no microchips required

Not really. Tests with two lines generally have one "control" line and one "test" line. If the control line fails to appear, then the result is invalid and you should try a new kit, regardless of what the other line said. If the control line appears, then the result is valid and the test line shows a negative (no line) or positive (line) result. So "pregnant" should only appear if both lines show up. It's a very simply boolean AND condition, but that's something that would be challenging to have done purely by chemical reaction. Probably a lot more complex than having a simple check by a circuit. Using a microprocessor, you can have "pregnant", "not pregnant" or "invalid" show up to give an unambiguous single result. Trying to achieve the same through chemical means only is likely also more prone to failure. Even if the outcome is clear, there are still false positives and negatives. Of course you should expect users to read the manual and be capable of interpreting a very simple system with only 4 combinations and 3 outcomes, but apparently that's beyond many people. Which is exactly why some test producers go to this length.

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