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
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