Do we need BQL?

From: "Stephen Duffull" <sduffull@fs1.pa.man.ac.uk> Subject: Do we need BQL? Date: Tue, 3 Aug 1999 09:51:06 +0100 Dear NM Users I read with continued interest the discussion about BLQ (BQL, LOQ, BLT ...). I thought that I might add something for more general discussion. BLQ to me is an assay artefact. It has no specific clinical or modelling value and as far as I can tell is arbitrary (although most publications seem to recommend the same cut-off value). If BLQ was never reported, but rather the "observed" concentration was reported instead, then this would make sense from a modelling perspective. We can then let the likelihood compute the appropriate contribution of each concentration (assuming an appropriate error model has been chosen). The important assay parameter "limit of detection" which does have specific meaning in a modelling context (although its value is still arbitrary), would continue to be of interest. I realise that this is of no help to the discussion about what to do with BLQs, but perhaps this problem is somewhat self-induced. Regards Steve ===================== Stephen Duffull School of Pharmacy University of Manchester Manchester, M13 9PL, UK Ph +44 161 275 2355 Fax +44 161 275 2396