PHASES risk prediction score

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 haemorrhage, 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.

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