Roger Ekins and the acb list
Roger has placed me in the limelight - that I do not deserve - because of
'sensitivity'.
I admit having worked with the IFCC and IUPAC for quite some time but I am
not involved in this issue. I cannot explain how the discussions and
deliberations have gone backwards and forwards in the representative groups
or during the consensus procedure but nevertheless feel obliged to make a
comment.
Like everybody else I understand we need two concepts, one describing the
smallest concentration that a particular measurement procedure can measure
as different from 0 - or a blank. That is called detection concentration
(limit) and the detectability of the procedure. I am aware of the
discussions, but not involved, on how the detection limit should be best
defined - which is not too simple to agree upon.
The other deals with a common question that we are confronted with: how
small differences can the measurement procedure differentiate? This is
defined as the analytical sensitivity. I am aware of the fact that it is not
only the slope of the calibration curve that will define the least
noticeable or reportable difference but also the uncertainty of the
measurement. Diagnostic sensitivity is of course quite different
I do not believe that the BIPM etc definition is contrary to that of
colloquial English. My Oxford dictionary is only a Paperback but also a
"Thesaurus and Wordpower Guide" and I cite the first explanation of
sensitive: "quick to detect or be affected by slight change".
The bottom-line is that we have two concepts and two terms, both defined and
none jeopardising a common interpretation of "sensitivity". Let us accept
them and use them properly!
Anders Kallner
PS We have not done away with "accuracy". Its proper use is slowly making
headway into clinical chemistry but still seems confused with trueness by
some authors.
Anders Kallner MD PhD
Dept Clinical Chemistry
Karolinska University hospital
SE 171 76 Stockholm, Sweden
Phone: +46 8 5177 4943
Fax: +46 8 5177 2899
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