After 35 cycles, you have 32 billion copies. If you can't detect 32 billion copies, something has gone horribly wrong.
If you go to 42 cycles, 4 trillion copies, and you've got a signal, that signal is an error. The process itself created some debris that matches the target profile, and that debris is now getting replicated, but it wasn't originally in the sample, so it shows up late, which puts the curve behind expectations.
PCR testing requires an absolute commitment to proper procedure and absolute attention to detail. If you rush it, if you cut corners, if you are working 14 hour days because you've got millions of these tests to run, if you don't normally do biolab stuff but watched a 2 hour training video because they needed lab techs, you will fuck up. And a fucked up test is worse than no test at all - in both cases, you don't know anything, but in one of those cases, you think that you do.
PCR doubles the sample every cycle.
After 35 cycles, you have 32 billion copies. If you can't detect 32 billion copies, something has gone horribly wrong.
If you go to 42 cycles, 4 trillion copies, and you've got a signal, that signal is an error. The process itself created some debris that matches the target profile, and that debris is now getting replicated, but it wasn't originally in the sample, so it shows up late, which puts the curve behind expectations.
PCR testing requires an absolute commitment to proper procedure and absolute attention to detail. If you rush it, if you cut corners, if you are working 14 hour days because you've got millions of these tests to run, if you don't normally do biolab stuff but watched a 2 hour training video because they needed lab techs, you will fuck up. And a fucked up test is worse than no test at all - in both cases, you don't know anything, but in one of those cases, you think that you do.
Thanks for explaining. I had no clue what 'cycles' mean in this context.
BTW, some tests are said to give results within 15 minutes. How long does each 'cycle' typically take?
Do we know nationally how many tests were counted positive but had >35 cycles?