Table 3.

Performance of the Ottawa subarachnoid haemorrhage rule and Emerald subarachnoid haemorrhage rule

Total cohort, n=366Subgroup, n=65a
SAH presentSAH absentSAH presentSAH absent
Ottawa rule positive16272449
Ottawa rule negative078012
Emerald rule positive13254444
Emerald rule negative3b96017
SensitivitySpecificitySensitivitySpecificity
Ottawa rule100%22%100%20%
Emerald rule81%27%100%28%

  • ↵a = subgroup of patients with maximum headache intensity within 1 hour;

  • ↵b = two cases of subarachnoid haemorrhage were identified on computed tomography of the head, and one case was identified on lumbar puncture; SAH = subarachnoid haemorrhage.