Dear list members!
The lowest detectable difference for a quantitative method (LDD (%))has been
explained to me to be LDD (%) = 2.8 * total CV (%). This is also used to define
the limit of detection for a method. My wonder is what the conditions are for
applying this. Can this be applied also when CV reaches 30 %? CVs in this range
would than mean that two quantitative values can be discriminated with 95%
confidence when the higher value is twice the lower value. My feeling is that
the equation does not take in acount the increase in standard deviation of the
error with higher values, which is inherent in our methods and that the
distribution of the error is likely to have a positive skewness when CV is high.
I would also appreciate references over this matter.
With kind regards
Goran Brattsand
M.D.
Clinical Chemistry
Umeå University Hospital
S-901 85 Umea
Sweden
e-mail : <[log in to unmask]>
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