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Dear all:
I just want to inquire two question about the comments of the reviewer.
The
reviewer suggested that "within-day and day-to-day imprecision" should
be
concluded, however, we investigated the "within-day and day-to-day
precision"
via the way of "Precision and accuracy were determined by assaying six
replicates of each QC sample on three separate days using independently
prepared
calibration curves. Intra-day and inter-day precision were expressed by
the
relative standard deviation (RSD, %)", could you anyone give us some
suggestion?
Comments: As the FDA guidance for bioanalytical method validation is
followed
(reference [18]), the authors need to clearly differentiate between
within-day
and day-to-day imprecision. In terms of inter-day imprecision, due to
the
multiple repetitions of each sample per day on relatively few days
(n=6/day for
3 days), between-run variability cannot simply be estimated by
calculating RSD%
across the whole data set for each compound/concentration. The simple
calculation of RSD% across all data for each QC level will underestimate
between-run imprecision since it increases the number of observations
and thus
potentially lowers the standard deviation. For more details, please see:
Krouwer
J S, Rabinowitz R (1984). How to improve estimates of imprecision. Clin
Chem 30:
290-292. To determine inter-day imprecision correctly, the authors
should follow
the strategy as outlined in Clinical Laboratory and Standards Institute
(CLSI;
www.clsi.org) document EP05-A2, as this is the most robust strategy and
is
increasingly accepted as the standard for determining inter-day
imprecision.
I am looking forward to hearing from you soon.
Beat wishes!
Longshan Zhao
Shenyang Pharmaceutical University
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