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Comments: To: "Mainwaring-Burton Richard (RGZ)"          <[log in to unmask]>
Subject: Re: sensitive issues[Scanned]
Date: Thu, 3 Apr 2008 18:06:12 +0100
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Thread-Topic: sensitive issues[Scanned]
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From: "Roger Ekins" <[log in to unmask]>
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Richard (et al),

Well I don't think the number of decimal places used in expressing assay =
results is a critical issue, though I would hope that ACB members are =
well-enough scientifically trained to quote only =
statistically-significant figures.

In my opinion manufacturers should include with their assay products =
simple (within-assay) precision profiles (essentially as shown in my =
figure)  which would provide their customers with sufficient information =
to assess the precision of the system  within the range of values in =
which they are individually interested (as well as the system's =
sensitivity). Between assay (or inter-assay) precision profiles  would =
also be useful (because other error components are likely to be =
implicated),  but is a bit of a luxury, and perhaps too much to expect =
at this stage.

Clinical chemists may, of course, choose to run samples within an assay =
in duplicate or triplicate (which is what I and my colleagues did when =
we were providing hormone assays throughout the UK for the Supraregional =
Assay Service; however  we were using in-house assays and reagents, and =
the extra costs involved in so doing  were negligible), in which case I =
would hope that they could appropriately  modify the results that they =
supply to the clinicians to whom they report. The latter should also be =
notified, not only of the confidence levels of the results with which =
they are provided (something with which I agree with Aubrey),  but also =
of the assay system used by the assayist, since the majority of =
substances assayed by clinical chemists are not chemically defined, in =
which circumstance results are almost certain to be method-dependent.

But the first thing is to ensure that clinical chemists (consultants or =
otherwise) should know what they mean by sensitivity, precision, bias =
and accuracy, of which concepts some clinical chemists (in my =
experience) have often been woefully ignorant.

Roger Ekins =20





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Having started this thread, I now wish I hadn't, although I have =
acquired sufficient reading material to last me well into my retirement. =
(Thanks Roger and Westgard via Jonathan)

=20

No doubt at the end of it I will feel much better educated about =
sensitivity, and have already resolved not to post a similar question on =
1st April next year about specificity.

=20

Nonetheless would it not be simpler and fairer to all for the =
manufacturers (any Corporate members listening ?) to itemize somewhere =
within their usually excessive amounts of kit insert data, simple =
justifiable figures which we can use as evidence-based, properly derived =
data for :

1.       number of reportable decimal places (at different levels if =
necessary)

2.       suitable figure we can claim as lowest sensible reportable =
value

This would not necessitate reams of paper but simple adherence to the =
same parameters, probably defined somewhere in the reading material, but =
agreed between the manufacturers and the profession.

I seem to recall in by-gone days a quoted parameter which was the =
"smallest amount distinguishable from zero" but that requires the =
decimal place argument to be involved. Is zero =3D 0, 0.0, 0.00 or even =
0.000 ?

=20

During the course of current discussion, it has come to light that =
different laboratories using the same equipment are quoting different =
lower limits of detection and decimal places for the same analyte, in =
particular PSA.  I have a concern that some not so scrupulous might =
claim the favour of the urologists, simply by quoting different figures.

=20

Anyone want to do an audit of decimals and tumour markers across =
laboratories/equipment ?

with best wishes
Richard
Richard Mainwaring-Burton
Consultant Biochemist
Queen Mary's Hospital
Sidcup, Kent

020-8308-3084


--=20

Prof Roger Ekins,  PhD DSc FRS

Molecular Endocrinology,
Windeyer Institute
University College London
London W1T 4JF


Phone +44 20 7679 9410
Fax +44 20 7679 9407
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biochemistry. Please note, archived messages are public and can be =
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blockquote, dl, ul, ol, li { padding-top: 0 ; padding-bottom: 0 }
 --></style><title>Re: sensitive issues</title></head><body>
<div>Richard (et al),</div>
<div><br></div>
<div>Well I don't think the number of decimal places used in
expressing assay results is a critical issue, though I would hope that
ACB members are well-enough scientifically trained to quote only
statistically-significant figures.</div>
<div><br></div>
<div>In my opinion manufacturers should include with their assay
products simple (within-assay) precision profiles (essentially as
shown in my figure)&nbsp; which would provide their customers with
sufficient information to assess the precision of the system&nbsp;
within the range of values in which they are individually interested
(as well as the system's sensitivity). Between assay (or inter-assay)
precision profiles&nbsp; would also be useful (because other error
components are likely to be implicated),&nbsp; but is a bit of a
luxury, and perhaps too much to expect at this stage.</div>
<div><br></div>
<div>Clinical chemists may, of course, choose to run samples within an
assay in duplicate or triplicate (which is what I and my colleagues
did when we were providing hormone assays throughout the UK for the
Supraregional Assay Service; however&nbsp; we were using in-house
assays and reagents, and the extra costs involved in so doing&nbsp;
were negligible), in which case I would hope that they could
appropriately&nbsp; modify the results that they supply to the
clinicians to whom they report. The latter should also be notified,
not only of the confidence levels of the results with which they are
provided (something with which I agree with Aubrey),&nbsp; but also of
the assay system used by the assayist, since the majority of
substances assayed by clinical chemists are not chemically defined, in
which circumstance results are almost certain to be
method-dependent.</div>
<div><br></div>
<div>But the first thing is to ensure that clinical chemists
(consultants or otherwise) should know what they mean by sensitivity,
precision, bias and accuracy, of which concepts some clinical chemists
(in my experience) have often been woefully ignorant.</div>
<div><br></div>
<div>Roger Ekins&nbsp; </div>
<div><br></div>
<div><br></div>
<div><br></div>
<div><br></div>
<blockquote type=3D"cite" cite>Content-Type: text/html<br>
X-MIME-Autoconverted: from 8bit to quoted-printable by
bofur.jiscmail.ac.uk id m33Fdr5E009763<br>
</blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">Having started this thread, I now wish I hadn't,
although I have acquired sufficient reading material to last me well
into my retirement. (Thanks Roger and Westgard via
Jonathan)</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">&nbsp;</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">No doubt at the end of it I will feel much better
educated about sensitivity, and have already resolved not to post a
similar question on 1st April next year about
specificity.</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">&nbsp;</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">Nonetheless would it not be simpler and fairer to all
for the manufacturers (any Corporate members listening ?) to itemize
somewhere within their usually excessive amounts of kit insert data,
simple justifiable figures which we can use as evidence-based,
properly derived data for :</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">1.</font><font face=3D"Times New Roman" size=3D"-2"
color=3D"#000080">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</font><font
face=3D"Arial" size=3D"-1" color=3D"#000080"> number of reportable =
decimal
places (at different levels if necessary)</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">2.</font><font face=3D"Times New Roman" size=3D"-2"
color=3D"#000080">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</font><font
face=3D"Arial" size=3D"-1" color=3D"#000080"> suitable figure we can =
claim
as lowest sensible reportable value</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">This would not necessitate reams of paper but simple
adherence to the same parameters, probably defined somewhere in the
reading material, but agreed between the manufacturers and the
profession.</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">I seem to recall in by-gone days a quoted parameter
which was the &quot;smallest amount distinguishable from zero&quot;
but that requires the decimal place argument to be involved. Is zero =3D
0, 0.0, 0.00 or even 0.000 ?</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">&nbsp;</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">During the course of current discussion, it has come
to light that different laboratories using the same equipment are
quoting different lower limits of detection and decimal places for the
same analyte, in particular PSA.&nbsp; I have a concern that some not
so scrupulous might claim the favour of the urologists, simply by
quoting different figures.</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">&nbsp;</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-1"
color=3D"#000080">Anyone want to do an audit of decimals and tumour
markers across laboratories/equipment ?</font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" =
color=3D"#000080">with
best wishes</font><font color=3D"#000080"><br>
<font face=3D"Monotype Corsiva" size=3D"+3">Richard</font></font><font
color=3D"#000080"><br>
<font face=3D"Arial" size=3D"-1">Richard
Mainwaring-Burton</font></font><font color=3D"#000080"><br>
<font face=3D"Arial" size=3D"-2">Consultant =
Biochemist</font></font><font
color=3D"#000080"><br>
<font face=3D"Arial" size=3D"-2">Queen Mary's =
Hospital</font></font><font
color=3D"#000080"><br>
<font face=3D"Arial" size=3D"-2">Sidcup, Kent</font></font></blockquote>
<blockquote type=3D"cite" cite><font face=3D"Arial" size=3D"-2"
color=3D"#000080">020-8308-3084</font></blockquote>
<div><br></div>
<x-sigsep><pre>--=20
</pre></x-sigsep>
<div><br>
Prof Roger Ekins,&nbsp; PhD DSc FRS<br>
<br>
Molecular Endocrinology,</div>
<div>Windeyer Institute<br>
University College London<br>
London W1T 4JF<br>
<br>
<br>
Phone +44 20 7679 9410<br>
Fax +44 20 7679 9407</div>
</body>
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------ACB discussion List Information--------
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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.
ACB Web Site
http://www.acb.org.uk
List Archives
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List Instructions (How to leave etc.)
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