People are always a little confused about analytical validation characteristics like accuracy, precision, intermediate
precision, repeatability and reproducibility. Can some differentiate these to terms?
Accuracy is defined as the degree of exactness, and precision
means the degree of reproducibility.
Accuracy
The
accuracy of an analytical procedure expresses the closeness of agreement
between the value which is accepted either as a conventional true value or an
accepted reference value and the value found. This is sometimes termed
trueness.
Precision
The
precision of an analytical procedure expresses the closeness of agreement
(degree of scatter) between a series of measurements obtained from multiple
sampling of the same homogeneous sample under the prescribed conditions.
Precision may be considered at three levels:
repeatability, intermediate precision and reproducibility. Precision should be
investigated using homogeneous, authentic samples. However, if it is not possible
to obtain a homogeneous sample it may be investigated using artificially prepared samples or a sample solution. The precision of
an analytical procedure is usually expressed as the variance, standard deviation
or coefficient of variation of a series of measurements.
Repeatability
Repeatability
expresses the precision under the same operating conditions over a short interval
of time. Repeatability is also termed intra-assay precision.
Intermediate precision
Intermediate
precision expresses within-laboratories variations: different days, different analysts,
different equipment, etc.
Reproducibility
Reproducibility
expresses the precision between laboratories (collaborative studies, usually
applied to standardization of methodology).
