Dear Andy and Jonathan
Within-assay replication decreases the within-run component of variation by
a factor related to the square root of the number of replicates. It does not
affect the between-run and between-laboratory components of variation.
It was widely used in bioassays and radioimmunoassay, but the primary use
was to detect blunders and fliers; not to reduce imprecision.
Best wishes
Gordon Challand
----- Original Message -----
From: "Jonathan Kay" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, March 23, 2010 11:12 AM
Subject: Re: Manually improving precision?
Analysis in duplicate was common in immunoassay and some other methods until
very recently. My feeling is that it was done more to catch blunders and
flyers than to improve precision.
Where are people currently using duplicate in clinical assays?
Jonathan
On 22 Mar 2010, at 15:47, Andy Minett wrote:
> Dear All,
>
> I have recently been reading about the tightening of quality requirements
> in
> proficiency testing for glycated haemoglobin in America
> (http://james.westgard.com/the_westgard_rules/2010/02/gutcheck-
> hba1c.html ). One of the issues raised here is that many platforms do not
> deliver the necessary imprecision to meet current quality requirements,
> let
> alone future improvements.
>
> In fear of making a rather banal suggestion, has anyone looked at
> “manually”
> (elaboration below) reducing the imprecision of an analyser? In fact, I am
> so
> sure this approach has been considered and rejected, the question I am
> really
> asking is: what are the drawbacks of this approach, and can the mailbase
> provide me with references that discuss it (my own searches have been
> unfruitful).
>
> By “manually reducing imprecision” what I mean is taking multiple
> simultaneous
> readings and reporting the average of those as the test result. In an
> unrelated
> (i.e. not Biochemistry related) mathematical project, I needed to find a
> way of
> minimising the scatter of data from a Normal Random number generator with
> fixed Mean and CV. Through mass data testing I calculated the reduction in
> scatter (CV) to be closely estimated by:
>
> % reduction in CV = (1-1/(n^0.5)) * 100
>
> (where n = number of replicate measurements averaged)
>
> Using this in my project, I was able to reduce the CV of the number
> generator
> by 80% by averaging 25 results from it.
>
> Imagining a hypothetical glycated haemoglobin analyser that has a stable
> CV
> of 3% say, taking the average of 4 simultaneous analyses of each sample
> would reduce the CV of the method by 50%; to 1.5%.
>
> What are the drawbacks to using this approach in blood analysis? Other
> than
> the approach being n times as costly as single-result analysis.
>
> Best regards,
> Andy Minett
>
> ------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
> Green Laboratories Work
> http://www.laboratorymedicine.nhs.uk
> List Archives
> http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
> List Instructions (How to leave etc.)
> http://www.jiscmail.ac.uk/
------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
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
------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
Green Laboratories Work
http://www.laboratorymedicine.nhs.uk
List Archives
http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html
List Instructions (How to leave etc.)
http://www.jiscmail.ac.uk/
|