The incidence rate for aneurysm detection in different risk groups
| Group | Aneurysm detection | |
| n/N | IR (95% CI) | |
| Low risk* | 1/80 | 1.250 (0.176 to 8.874) |
| intermediate risk* | 9/138 | 6.522 (3.393 to 12.534) |
| high risk* | 11/54 | 20.370 (5.034 to 36.783) |
| Overall | 21/272 | 7.721 (5.034 to 11.841) |
*The patients were stratified into three groups according to the presence of two risk factors (NPAN-SAH and mFS 3–4): the low-risk group was without any of the two risk factors, the intermediate-risk group only had one risk factor, and the high-risk group had >1 risk factor.
IR, incidence rate; mFS, modified Rankin Scale; N, total number in the corresponding group; n, number of events; NPAN-SAH, non-perimesencephalic angiogram-negative subarachnoid haemorrhage.