Select this option to normalize the data using the formula: normalized value = (
log
(
x
) -
log
(
GM
))/
log
(
GSD
), where
x
is the raw value,
GM
is the geometric
mean
of the upper limit of the normal range (ULN) of values and the lower limit of the normal range (LLN) of values, and
GSD
is the geometric
standard deviation
of the ULN and LLN. The geometric normalized data are measured on a scale (centered on 0) based on the number of
GSD
units the observations are from
GM
.
On this scale the
GM
is the midpoint between the
log
transformed upper and lower limits (ULN and LLN) and each
GSD
is equal to half the range between the
log
(ULN) and
log
(LLN). With this normalization, values -1 and 1 are set to equal the LLN and ULN respectively and behave similar to a
z
-score. Clinically, values greater than 1 (or less than -1) can be interpreted as a measure of how far away the finding was from the ULN (or LLN) with respect to the normal range of values (ULN - LLN). Values less than 1 or greater than -1 would indicate that the finding was within the normal range of values.