The PHASES risk prediction score is a method of calculating the absolute 5-year risk of intracranial aneurysm rupture based on the data pooled from prospective cohort studies in the USA, Canada, Netherlands, Finland and Japan1. PHASES stands for: Population, Hypertension, Age, Size, Earlier subarachnoid hemorrhage, and Site.
Parameters
The score is calculated based on six statistically significant risk factors, the points for which are weighted based on individual hazard ratios.
Population (P)
- 0: North American, European (other than Finnish)
- 3: Japanese
- 5: Finnish
Hypertension (H)
- 0: no
- 1: yes
Age (A)
- 0: <70 years
- 1: ≥70 years
Size of aneurysm (S)
- 0: <7.0 mm
- 3: 7.0–9.9 mm
- 6: 10.0–19.9 mm
- 10: ≥20 mm
Earlier SAH from another aneurysm (E)
- 0: no
- 1: yes
Site of aneurysm (S)
- 0: ICA
- 2: MCA
- 4: ACA/Pcom/posterior circulation
Important points
The 5-year absolute risk of rupture based on score is currently estimated to be:
- ≤2 points: 0.4%
- 3 points: 0.7%
- 4 points: 0.9%
- 5 points: 1.3%
- 6 points: 1.7%
- 7 points: 2.4%
- 8 points: 3.2%
- 9 points: 4.3%
- 10 points: 5.3%
- 11 points: 7.2%
- ≥ 12 points: 17.8%
The PHASES score has since also been used to suggest that aneurysm growth may be an appropriate surrogate outcome measure of aneurysm rupture for studying risk prediction or intervention 2.