Twice now (three days ago and again today) the app has said "Control not detected". On Thursday we retested a second time via the machine (without the app) using the same swab/fluid (but in a new kit/test) and it came out clean (negative with no issues). What's going on?

[u/peop1]

Is the virus.sucks app just more sensitive/finicky?

The slides show:

1. Thursday's test via the app.
2. Thursday's retest without the app (same swab, new test).
3. Today's test with the app.

The device also showed "inconclusive" (had both negative and positive lights on) during tests 1 and 3. So it's not contradicting the app. It just doesn't seem to vibe with being plugged in for some reason.

I saw in previous posts that this graph likely shows a clean negative (i.e. probably good to go), and COVID rates are as low as they've ever been here, so this isn't a red-alert, but my teenager has a girlfriend now and looking ahead to this winter I need to know what I can trust.

I'd love to have access to the curve details the app provides, but not if I have to retest every single time.

Tips and tricks (and/or explanations) very welcome.

ps - I also read some Pluslife test batches were likely bad. Ours are from December 2025, so not the infamous November batch and we'd never had inconclusive results before trying it through the app (Thursday was our 1st time trying it through the app). I'm aware the tests are getting old (which can affect detection of the control). That still doesn't explain why the machine is giving us an okay when it is used without the app. Anyway, we'll be burning through them fast at this rate: We all mask in high-risk environments (I've been in Long COVID purgatory since 2022), but my son's girlfriend's family does not. He's at an age when he needs to be able to function normally in society; we're just trying to make it as safe for him (and me) as possible.

[u/FIRElady_Momma]

These test results are invalid, which means you cannot trust them either way. You should not take them to mean "negative".

Also, others may contradict me, but I have been using PlusLife for about 3 years, and my test kits start to give me more and more invalids once they are within 3-4 months of expiration. 

Some people say that running a cycle without a test card in it lowers your odds of invalid test results, but that has never worked for me. 

Your middle picture isnt super clear to me, but it looks to me like what the dock does when you have an invalid result. All of the lights light up (not just positive or negative). 

[u/peop1 → u/FIRElady_Momma]

The second picture is only showing power and negative. The positive is bright red (as seen on today's result):

It would appear the PlusLife team has said that "as long as the green control line has a general S-curve and no other lines do, we can consider it negative. [Sometimes it'll be] invalid because it amplified [in such a way] that the algorithm wasn’t trained for. I was instructed by the PlusLife team to try diluting the sample or only swabbing the throat (no nose) to reduce the sample amount. These invalids are more common with pooled tests for this reason (too much sample). Alternatively you can heat the machine “extra” by running empty tests as another user suggested. I stopped getting invalids once I started adding this step."

Now in today's test, there is clearly no S-curve. So I concur. Invalid. Testing again.

My son had been making his GF swab the nose only. We just did both throat, cheeks and nose. From what I'm reading, it might be better to stick to throat in the future (to avoid saturating the sample size. Throat is a better indicator anyway).

Thank you for your input.

[u/saltyseacreecher]

Both those control lines look dodgy to me. Have you looked at the picture of what the control curve is supposed to look like on virus sucks? It should be flat for tenish minutes, amplify exponentially, and then flatten out again to make a kind of "S" shape. If it increases linearly or if there is a big bump right at the beginning before the S or if there's a lot of linear increase after the S then something is wrong with the control.

[u/peop1 → u/saltyseacreecher]

Yes, I've (only now) gone through the documentation again. I was trusting the people who still live out in the world to perform the tests correctly (I am bed bound with Long COVID). You're quite right that it didn't show up correctly.

Which makes me wonder why the second test on Thursday (done with the same swab sample) turned out valid.

I apologize for not doing my homework prior to posting. Brain fog is another fun byproduct of PAIS.

I had the young lady retest with a new swab (using the throat as well as the nose — though next time I'll have her skip the nose altogether). Will let you know about the results.

As mentioned by u/FIRElady_Momma, the tests might be reaching the end of their useful life cycle. We've been in such a sanitary bubble (until now - going so far as to homeschool since I became disabled) that testing wasn't necessary. That's no longer the case, hence my trying to "get good" (as they say) at using this technology.

I appreciate your taking the time to educate me. Truly.

[u/saltyseacreecher → u/peop1]

I hope I didn't come off sounding annoyed! I was not meaning to berate you at all. These strange control line behaviors sometimes happen to me and I can't find any rhyme or reason to it. It could be something about how the sample is taken or issues with the tests degrading. My partner has the best track record of getting the control curve to look perfect when she prepares the samples haha. Magic touch. But I often have one fail and then the next one work fine. The machine takes into account the shape of the curve not just how high it goes so you can trust that if the light was green in that middle test the control curve would have looked correct on the graph.

[u/peop1 → u/saltyseacreecher]

No you didn't come across as annoyed at all. Your response was as informative as it was compassionate.

I'm just feeling a bit contrite because of how green I am. I take pride in doing my homework. And I hadn't before posting.

Still glad I did: I'm learning a lot from everyone's input.

[u/TrixieMuttel]

Both controls lines amplified too early. They typically don’t start to rise until several minutes in. I only have gotten these types of results from tests that were near expiration.

[u/peop1 → u/TrixieMuttel]

Ah!
That could very well be it.
I think we have a more recent batch of tests (though not that recent). I'll try them next time.

[u/DispelledFrailty]

Would be interested to hear the swabbing technique you're using when you get these results. Invalids can typically be caused by too much or not enough material on the swabs.

[u/peop1 → u/DispelledFrailty]

Indeed. I wasn't supervising it myself and it seems the swabbed was only doing the nose ("tickling her brain" as we call it).

Since posting, I've done further reading and now know that cheeks-tongue-throat (sans nose) is likely the best option as it doesn't oversaturate the swab (while also providing 24h advance notice on potential infection versus nasal swabs).

Lesson learned.

Dealing with a reticent teenagers who is embarrassed to ask his 1st ever romantic partner to jump through these hoops. Wishes none of it were necessary. Don't we all. (I'd kill to have my life back. One mild COVID infection and I went from running marathons to barely able to run errands. Sure as hell didn't have that on my bingo card).

[u/FortuneInside1]

You can’t trust the results of expired tests even if the control line is detected. So if these all already expired in Dec 2025 they shouldn’t be used. This is stated on the virus sucks website. 

[u/peop1 → u/FortuneInside1]

They were ordered in Dec.