A comparison of two different assays for determining S-100B in serum and urine.
BACKGROUND
Brain injury after head trauma can be detected by S-100B measurements in serum. Recent preliminary studies indicate that urinary levels of S-100B are also increased after head injury, a finding that is of possible clinical value. The aims of the present study are two-fold: to compare serum measurements of two assays, the Liaison Sangtec 100 system and the Elecsys S100 test, and to investigate to what extent they can detect and measure S-100B in urine.


METHODS
A total of 191 serum and 174 urine samples from 107 patients (children aged between 1 and 18 years following head trauma) were measured with both assays. The results were compared using correlation analysis and Bland-Altman difference plots.


RESULTS
Serum values of the Sangtec system ranged from 0.02 to 2.28 microg/L, and from 0.005 to 2.13 microg/L for the Elecsys test. Comparisons showed a clear correlation (correlation coefficient 0.80) but not an agreement between the methods. The Sangtec system could only detect S-100B in 20 out of 174 urine samples (range 0.02-0.06 microg/L), whereas the Elecsys test could detect S-100B in 171 samples (range 0.005-0.14 microg/L). No clear relation was observed between the two methods in urine analysis (correlation coefficient 0.60).


CONCLUSIONS
The Sangtec and Elecsys assays are not interchangeable methods when analyzing S-100B in serum or urine samples after head injury.
Hallén
Magnus
M
Department of Surgery, Central Hospital Karlstad, Karlstad, Sweden.
Carlhed
Rickard
R
Karlsson
Mathias
M
Hallgren
Thomas
T
Bergenheim
Mikael
M
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007223:Infant; D009414:Nerve Growth Factors / Q000097:blood* / Q000652:urine*; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000097:blood* / Q000652:urine*
D009414:Nerve Growth Factors; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins