why are some positive lateral flow tests a faint line?

[ArianaG]

I understand that any line is still a positive but why are some faint and some stronger in colour? Is it to do with viral load or are the tests not that sophisticated?

I would assume that the intensity of line is relative to how well the test was conducted

Thank you, I thought this might be the case but can't seem to find any info on it.

I wondered if it was viral load or severity of illness. My LFT positive line was so faint it was barely there and, correspondingly, my symptoms are so slight they're barely there either.

I wondered that too @blameitonthecaffeine.
Did you get a positive PCR too?
However currently my dh and I both have positive LFTS, my dh had a dark line and mine was pale however he has less symptoms so far so not sure it works that way?

It's like a pregnancy test. Tthe darker the line, the more virus the test detected in the sample. That may be down to viral load, or it may be due to swabbing /extraction processing technique.

@blameitonthecaffeine

I wondered if it was viral load or severity of illness. My LFT positive line was so faint it was barely there and, correspondingly, my symptoms are so slight they're barely there either.

My Ds had an instant really bold line but only had a bit of a sore throat so don't think its to do with severity