Rapid antigen tests Sure. We've had 3 invalid tests, 5 positive and three of these confirmed positive with PCR. Hopefully its OK for me to share some MoH stats from pharmacy testing over the summer break - from memory they did 41,000 tests got 19 invalid, 26 positive of which 9 confirmed positive with PCR.
I find it useful to think about RATs as testing for being infectious rather than infected, like a canary in a mine - they give us a chance to find someone who is infectious before they show symptoms and hence reduce the exposure time to everyone else.