Normally the detection log detection limit is stated in the report. My report max limit detection varies from 1 to 10K - 50K normal cells reference back ground meaning ~ 4 log to -4.5 log. And this ratio is then multiply with a baseline factor to tie to IS scale.
Well, could ask what is the confirm limit of the detection in your lab... Anyway I guess you are doing great near to PCRU,,, congratulation or did you ask your doc if you could be considered PCRU ?
There are reports that on present PCR dectection limit on some normal healthy person could be - 7 or - 8 log meaning 1 cell in 10, 000, 000 to 100, 000, 000 normal cells. About 70% of normal people could be detected. But I do not know if this is due to our present technology limit of due to the sensitivity error is inherent in the detection method.
I know that DNA-PCR method is more senstive to RT-PCR or Nested PCR technic, nevertheless you could check out the method used in your lab and how confident if the detection method used with your doctor. The DNA-PCR method was used to detect some successfull STIM trial patients to check if for MRD, however only 1 or 2 still found to be still undetectable - PCRU. But most of them are detectable with DNA-PCR.