| Outcome | No. of studies | No. of patients | Mean difference (95% CI) | I2 |
|---|---|---|---|---|
| Mortality | ||||
| Evaluation time | ||||
| ICU | 0 | - | - | - |
| 1 mo | 3 | 66 | 33.09 (9.67 to 56.51) | 73 |
| 3 mo | 0 | - | - | - |
| 6 mo | 2 | 80 | - | - |
| 12 mo | 2 | 132 | - | - |
| Unclear | 3 | 84 | 22.71 (14.45 to 30.97) | 0 |
| Sampling time, hr | ||||
| Up to 12 | 5 | 336 | 15.11 (6.29 to 23.93) | 83 |
| Up to 24 | 5 | 138 | 22.86 (9.66 to 36.06) | 56 |
| Type of sample | ||||
| Venous | 5 | 253 | 25.53 (6.54 to 44.53) | 84 |
| Blood NS | 5 | 221 | 16.13 (7.63 to 24.62) | 65 |
| Biochemical analysis | ||||
| RIA | 4 | 83 | 23.89 (16.22 to 31.05) | 0 |
| LIA | 1 | 48 | - | - |
| ELISA | 3 | 271 | 6.12 (4.15 to 8.09) | 0 |
| ECLIA | 0 | - | - | - |
| Other | 2 | 72 | - | - |
| Minimal TBI severity | ||||
| Mild | 2 | 49 | - | - |
| Moderate | 2 | 125 | - | - |
| Severe | 6 | 268 | 13.30 (5.92 to 20.67) | 79 |
| Isolated TBI | ||||
| Isolated | 3 | 235 | 17.07 (0.29 to 33.85) | 88 |
| Nonisolated | 5 | 198 | 24.35 (9.70 to 39.00) | 81 |
| Unclear | 2 | 41 | - | - |
| GOS or GOSE | ||||
| Evaluation time | ||||
| ICU | 1 | 30 | - | - |
| 1 mo | 2 | 70 | - | - |
| 3 mo | 2 | 75 | - | - |
| 6 mo | 4 | 268 | 17.19 (4.82 to 29.55) | 87 |
| 12 mo | 1 | 48 | - | - |
| Unclear | 4 | 113 | 16.54 (7.85 to 25.22) | 52 |
| Sampling time, hr | ||||
| Up to 12 | 8 | 400 | 17.49 (9.76 to 25.22) | 85 |
| Up to 24 | 6 | 204 | 14.97 (5.80 to 24.14) | 71 |
| Type of sample | ||||
| Venous | 7 | 372 | 16.18 (8.41 to 23.95) | 87 |
| Blood NS | 7 | 232 | 16.13 (9.00 to 23.26) | 47 |
| Biochemical analysis | ||||
| RIA | 3 | 97 | 17.91 (12.59 to 23.23) | 0 |
| LIA | 1 | 48 | - | - |
| ELISA | 5 | 282 | 6.26 (4.31 to 8.20) | 79 |
| ECLIA | 1 | 34 | - | - |
| Other | 4 | 143 | 15.22 (10.74 to 19.70) | 83 |
| Minimal TBI severity | ||||
| Mild | 4 | 148 | 11.61 (4.99 to 18.32) | 46 |
| Moderate | 2 | 125 | - | - |
| Severe | 8 | 322 | 14.57 (7.36 to 21.77) | 83 |
| Isolated TBI | ||||
| Isolated | 6 | 346 | 13.80 (6.67 to 20.93) | 84 |
| Nonisolated | 7 | 226 | 22.42 (11.15 to 33.68) | 72 |
| Unclear | 1 | 32 | - | - |
Note: CI = confidence interval, CSF = cerebrospinal fluid, ECLIA = electrochemiluminescence immunoassay, ELISA = enzyme-linked immunosorbent assay, GOS = Glasgow Outcome Scale, GOSE = Glasgow Outcome Scale-Extended, ICU = intensive care unit, LIA = luminescence immunoassay, NS = not specified, RIA = radioimmunoassay, TBI = traumatic brain injury.