Whether we should be looking at PSA doubling rates has been looked at -e.g. http://hcp.prostateline.com/news/4176.aspx

But the similar assay-performance issues would arise.

Steve

 

-----Original Message-----
From: Mascall, Gary (Biochemistry) [mailto:[log in to unmask]]
Sent: 25 January 2005 11:20
To: [log in to unmask]
Subject: Re: Detection Limits for Assays

 

I think this originates from some studies done by DPC with their Ultrasensitive PSA method.

I know one of our Urologists uses this to assess whether patients who we report as having PSA <0.1 are still OK, or whether their level is rising.

 

I know DPC were keen to push this a few years ago, and we are currently collating results from the DPC assay against the Roche E170, to see if we can do them in-house.

 

Regards,

Gary

 

 

-----Original Message-----
From: Mainwaring-Burton Richard (RGZ) [mailto:[log in to unmask]]
Sent: 24 January 2005 10:47
To: [log in to unmask]
Subject: Detection Limits for Assays

I am having discussion with clinical colleagues regarding the lowest limit of detection for assays, in particular for PSA follow-up following radical prostatectomy, following a fairly acrimonious run-in with a very large Ozzie guy who had been told that if his PSA went above 0.004 his cancer might have returned. This had been quoted to him by his urologist in Sydney.

 

We use the Bayer Centaur (total PSA) which quotes

"Assay Range 0.01 to 100"

"sensitivity = 0.01"

low calibrator = 0

next value on the master calibrator = currently 1.03

 

Looking in the data sheet for Roche Elecsys 2010

"Assay Range 0.002 to 100"

"sensitivity = 0.002"

 

We curently report (Centaur) results to 1 decimal place, and thus register our lowest results as <0.1 whatever the Centaur says.

1. Am I being too harsh ?

2. Should we have a different reporting protocol for radical prostatectomies ?

3. Can we really trust these pretty extravagant claims for 'sensitivity'

4. What do other colleagues report as their lowest detectable/reportable result ?

 

Of course this does not only apply to PSA and I am interested how folks utilise the quoted sensitivities particularly for excludogram assays like tumour markers, troponin etc.  Do you swallow what the manufacturer says or apply some experrt logic?

 

Happy to report back to group.

 

with best wishes

Richard

Richard Mainwaring-Burton
Consultant Biochemist
Queen Mary's Hospital
Sidcup, Kent
DA14 6LT
020-8308-3084

 

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 ------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content.

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