Diagnostic performance of S100B
| Within 6 hours of head injury | Within 24 hours of head injury | |||
| CT+ | CT− | CT+ | CT− | |
| Median S100B, µg/mL (IQR) | 0.36 p<0.01*
(0.17–0.52) | 0.15 p=0.03†
(0.09–0.31) | 0.17 (0.11–0.39) | 0.11 p=0.04†
(0.07–0.22) |
| S100B >0.1, µg/mL | 15/133 | 81/133 | 29/265 | 131/265 |
| S100B <0.1, µg/mL | 1/133 | 36/133 | 6/265 | 99/265 |
| Sensitivity % (95% CI) | 93.8 (69.8 to 99.8) | 93.8 (69.8 to 99.8) | ||
| Specificity % (95% CI) | 30.8 (22.6 to 40.0) | 30.8 (22.6 to 40.0) | ||
| Negative predictive value % (95% CI) | 97.3 (84.2 to 99.6) | 97.3 (84.2 to 99.6) | ||
| Positive predictive value % (95% CI) | 18.1 (15.6 to 20.8) | 19.2 (16.4 to 22.2) | ||
| Theoretical CT reduction N (% (95% CI)) | 37/133 (27.1 (18.9 to 36.8)) | 105/265 (37.4 (32.0 to 47.2)) | ||
| Missed injury N (% (95% CI)) | 1/133 (0.75 (0.0 to 2.2)) | 6/265 (2.3 (0.5 to 4.1)) | ||
| Median time to blood draw Hours (IQR) | 4 (2.94–5.0) | 6.08 (4.0–10.0) | ||
Results were considered significant if p value was <0.05.
*Comparison of positive CT-head results between 6-hour and 24-hour groups.
†Comparison of those with positive and negative CT-head results within each group.