You could of course do what we (perhaps) should be
doing anyway.
Report results with a best-estimate and a 90%
analytical confidence limits (and perhaps a
biological confidence limit). The whole spurious
issue of sensitivity (and the fear of other labs)
would then reveal its red-herring head.
Aubrey
JM> This lesson from Jim's website might be helpful:
JM> http://www.westgard.com/lesson29.htm
JM> cheers
JM> J
JM> -----Original Message-----
JM> From: Clinical biochemistry discussion list
JM> on behalf of Mainwaring-Burton Richard (RGZ)
JM> Sent: Tue 01/04/2008 15:23
JM> To: [log in to unmask]
JM> Subject: sensitive issues
JM>
JM> Pardon my ignorance all
JM> I am struggling with the "sensitivity" of PSA
JM> and other similar assays.
JM> We use Abbott Architect Total PSA -
JM> (data sheet : Functional
JM> Sensitivity = 0.05, Analytical Sensitivity = 0.008)
JM> Colleagues with Roche Modular -
JM> (data sheet : Functional
JM> Sensitivity = 0.03, Analytical Sensitivity = 0.003)
JM> We both currently default to <0.1 as lower limit of detection.
JM> My questions for the clever guys (simplish answers please) are :
JM> 1. Are we being over cautious - could we
JM> claim a lower cut-off limit ?
JM> 2. What do I do when a Urologist has
JM> asked me to send the sample for an
JM> "advanced" PSA for post radical prostatectomy
JM> monitoring ? I am concerned
JM> that I may send the sample to someone using
JM> the same assays but different
JM> rules! (Our Architect reported result of 0.00)
JM> 3. What are the REAL meanings of
JM> functional and analytical
JM> sensitivities ? - I have read what it says in
JM> the data sheet, but would like
JM> understandable translation please.
JM> 4. How do we translate those into a
JM> reasonable and justifiable lower
JM> limit of detection ?
JM> 5. Yet again PSA - Provokes Stress and Anxiety.
JM> with best wishes
JM> Richard
JM> Richard Mainwaring-Burton
JM> Consultant Biochemist
JM> Queen Mary's Hospital
JM> Sidcup, Kent
JM> 020-8308-3084
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