PCR starts maximising positive always at 30 for short sequences. This is published and well known for almost 20 years. A gold standard would require a full unique long enough sequence. This is not usually possible to produce, let alone scale it. Without a gold standard the test has 4 possible logical results. Only subjective statistical methods could effectively deal with such scenarios under uncertainty. Impossible for the populace to understand the result is not binary and not possible to deploy at the individual level. FDA guidelines suggest to overcome this by limiting to 12 cycles. Usually luminescence is rendered quasi-mute at this cycle threshold for short sequences. The FDA relaxes said requirement to 18 cycles plus physician confirmation of symptoms. That's what Pfizer et al should have been doing in the polemic trials. But then again...