Does a badly administered swab test return no result or a negative result?

Factual Questions
1

When I recently took a covid test I had huge problems swabbing the back of my throat as I kept gagging. I was sure I did a poor job and the test came back negative. In hindsight I probably was negative but I wonder, if I had really failed to swab properly would I have simply returned a “no result”?

2

Totally anecdotal, but my barber told me that his nose bled immediately after a nurse administered the test, and he was in pain for days. She went in too deep and injured him. His test came back inconclusive. His wife and kids all got positive results. He finally took it again and it was positive.

3

Pretty sure the test returns positive if it finds viral DNA, and negative if it doesn’t. The reason for lack of viral DNA might be that there isn’t any in your body, or you didn’t do the thing to get the viral DNA in your body onto the swab, or any of some other things went wrong.

I don’t think there’s a “NULL” result for a covid test.

4

With nasal swabs, doing it wrong could decrease the sensitivity of the test (make it less likely to detect the virus). I’m not sure about throat swabs.

The main concern is that they got a good mucus sample from the back of your throat and not just saliva. Saliva testing is a thing, though. You would see “no result” if there was too little sample.

~Max

5

The university where I work just switched to saliva tests, and one of my staff got back a result that said:

“Your sample was rejected due to contamination present in the sample or due to non-conforming volume of sample. Please make arrangements with your test sponsor to submit a new sample as soon as possible.”

Instructions for the test say not to eat, drink, smoke, or brush your teeth for 60 minutes before testing.

6

The college where I work has been doing self-administered nasal swabs twice a week since late August. Once or twice, I’ve received an “inconclusive” result. They tell me this happens when the swab doesn’t pick up enough genetic material to run the PCR process on, or something like that.

7

There is a positive control for endogenous RNA in the human ribosome.

https://www.fda.gov/media/138818/downloadhttps://www.fda.gov/media/138818/download

In other words, if the PCR reaction does not show the presence of human ribosomal RNA - which it always should - that indicates that something has gone wrong in the protocol somewhere.

8

Ah so that answers it for sure - for that type of test anyhow.