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Klinisk Biokemi i Norden · 2 2015
In which patients and when should the S100B
analyses be performed?
It is important to note that the use of blood samp-
les for S100B as primary screening instead of CT is
recommended only for the group
“mild injury low-
risk”
. The aim of this strategy is to sort out patients
within this group with high S100B levels indicating
a possible intracranial injury. Only these patients
should undergo the secondary screening: a CT scan-
ning. There is every reason to assume that patients
in this group of
“mild injury low-risk”
constitute the
majority of patients with mild head injury, and we
estimate that the use of CT scanning can be reduced
by 30 % by replacing CT as the primary screening
procedure with the S100B test.
Only when the S100B analysis reveals a blood con-
centration ≥10 µg/L should a CT scan be performed.
If the S100B concentration is below that value, the
risk of missing an intracranial condition that needs
surgical treatment is very low.
Positive S100B results
The release of S100B into the blood is not confined
to “pure” head injuries; substantial extra-cranial
tissue damage, e. g. soft tissue contusions, may also
give increased blood values of S100B. We therefore
recommend that S 100B analyses is
not
used as scre-
ening procedure in the “mild injury low-risk” patients
with overt substantial extra-cranial tissue damage,
as
many of these patients will have increased S100B
results
. In such patients, a CT scan should be perfor-
med. It is important to remember that S100B should
only be used as a rule
out
test for patients with head
injuries (not as a rule
in
test).
False negative S100B results
Because S100B has a relatively short half-life in the
blood, we recommend that
only blood samples drawn
within the first 6 hours after the accident should be
analysed
. Samples drawn after that point may give
false negative results. If it proves impossible to obtain
Figure 1. Flow chart from the SNC guidelines for management of adult (≥18 years) patients with minimal, mild and mode-
rate head injuries.
