Re: Do we need BQL?

From: "Stephen Duffull" <sduffull@fs1.pa.man.ac.uk> Subject: Re: Do we need BQL? Date: Wed, 4 Aug 1999 09:20:01 +0100 James wrote: >BQLs returned from laboratories are unnecessary in pharmacokinetics, but >may have value in toxicokinetics. I agree that it is unnecessary in PK, but am not sure why TK would be any different? >I am sure the lab people would argue >that we really don't know (and can't determine) the behaviour of the assay >in this range. This may be a lab paradigm. I do not believe that the assay behaviour cannot be determined at this range. From my understanding BQL is often arbitrarily set to the concentration value when the CV% exceeds 20% (or sometimes some other value). I do not perceive the difference between a concentration measured with a CV of 19% vs one with a CV of 21%. What I perceive is needed is the best possible assay that the "lab people" can produce. Then all concs are reported irrespective of where they fall on the regression line and let the "modelling people" decide how to use them. Indeed Mats has suggested that the "modelling people" could work from peak areas and do not require the transformation to concentrations [I hope I have quoted you correctly here Mats.] > Fortunately most of us don't believe that the assay is all >that important compared to other sources of variation in the data and so >we couldn't care less. I don't think that this is the point. The contribution of assay error to the residual error variance can be easily handled without BQL. > The problem is that once we have BQLs we have >to deal with them But this shouldn't stop us thinking of where we might like to be in the future? Regards Steve ===================== Stephen Duffull School of Pharmacy University of Manchester Manchester, M13 9PL, UK Ph +44 161 275 2355 Fax +44 161 275 2396