GFAP and subarachnoid hemorrhage: Figure 1 presents the sample selection for this study, and the characteristics of the patients with available GFAP results in the Mild (Low Risk) group (n = 49) are presented in Table 1. Of these 49 patients, 36 (73.5%) underwent head CT scanning and 4 (11.1%) had acute CT abnormalities. The most common CT abnormality was traumatic subarachnoid hemorrhage (8.3%; n = 3).