3 replies to this topic

[dinasperrys]

Dear All

This is a question for the Maths wizards!

I have just had a PCR back at 3.9 log [yes, I'm delighted - best result I've had yet :-) ] but my haematologist says the lab cannot report over 4 log. He thinks the sensitivity of the lab is 1/100,000. Is this right? Surely if it was 1/100,000 then they could report up to 5 log?? Or is my maths wonky??

Happy New Year to all, and may we all see lots of zeros in 2011!

Jan

[Trey]

It is not so much a math issue, but rather a matter of practicality meets lawyers.  Most PCRs today can measure "up to 1/1,000,000".  But the science of PCRs is fuzzy, so most labs advertise "1/100,000" to be conservative.  This would allow -5 log reporting.  Some labs will report up to -5 log, but others stop at -4 log because PCRs are not as accurate as the decimal point would suggest.  So it depends on whether your specific lab reports beyond -4 log or stops at -4 log.  Beyond -4 log some just say the sample was positive but the assay was below the sensitivity levels of the test.  Others report out to 6 decimal places, which is a bit silly.

[cousineg]

You can obtain some information (videos) about  PCR sensitivity at http://www.cmleukemi...n-reaction.html

[dinasperrys]

Thank you both for your replies. I might have guessed that it would not be as simple as just applying a  mathematical principle! :-)

Jan