Clearly the test line binds some component of the coronavirus, I believe most commonly the nucleocapsid protein (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8049777/). However, despite extensive googling (and Google is doing a lousy job of understanding my question) I have not been able to figure out what is being bound by the control line. Probably it differs by test manufacturer, but I'm sure there are some relatively common antibodies that are used in the control line?
My best guess is that it should test for some common mucin or collagen or elastin but this is based on nothing.
The reason I'm asking is that I want to understand if the "control" line being present is a good indicator of the test having been done properly. Let's say some person:
- rubs the swab on a different body part than the nasal mucosa
- or doesn't touch the body at all with it
- or swabs the nasal mucosa very briefly
- or only inserts the swab into the buffer solution extremely briefly
would the control line still show up?
I'm not simply trying this myself at home because it's annoying and expensive to get lots of tests simply to waste them to test their limits.