title: Development of the PHASES score for prediction of risk of rupture of intracranial aneurysms: a pooled analysis of six prospective cohort studies.
abstract: BACKGROUND
  The decision of whether to treat incidental intracranial saccular aneurysms is complicated by limitations in current knowledge of their natural history. We combined individual patient data from prospective cohort studies to determine predictors of aneurysm rupture and to construct a risk prediction chart to estimate 5-year aneurysm rupture risk by risk factor status.
  
  
  METHODS
  We did a systematic review and pooled analysis of individual patient data from 8382 participants in six prospective cohort studies with subarachnoid haemorrhage as outcome. We analysed cumulative rupture rates with Kaplan-Meier curves and assessed predictors with Cox proportional-hazard regression analysis.
  
  
  RESULTS
  Rupture occurred in 230 patients during 29,166 person-years of follow-up. The mean observed 1-year risk of aneurysm rupture was 1·4% (95% CI 1·1-1·6) and the 5-year risk was 3·4% (2·9-4·0). Predictors were age, hypertension, history of subarachnoid haemorrhage, aneurysm size, aneurysm location, and geographical region. In study populations from North America and European countries other than Finland, the estimated 5-year absolute risk of aneurysm rupture ranged from 0·25% in individuals younger than 70 years without vascular risk factors with a small-sized (<7 mm) internal carotid artery aneurysm, to more than 15% in patients aged 70 years or older with hypertension, a history of subarachnoid haemorrhage, and a giant-sized (>20 mm) posterior circulation aneurysm. By comparison with populations from North America and European countries other than Finland, Finnish people had a 3·6-times increased risk of aneurysm rupture and Japanese people a 2·8-times increased risk.
  
  
  CONCLUSIONS
  The PHASES score is an easily applicable aid for prediction of the risk of rupture of incidental intracranial aneurysms.
  
  
  BACKGROUND
  Netherlands Organisation for Health Research and Development.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands. Electronic address: j.p.greving@umcutrecht.nl.
authors.forename: Jacoba P
authors.initials: JP
authors.lastname: Greving
authors.affiliation: Department of Neurology, Leiden University Medical Center, Leiden, Netherlands.
authors.forename: Marieke J H
authors.initials: MJ
authors.lastname: Wermer
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Brown
authors.affiliation: UCAS Japan Coordinating Office, University of Tokyo, Tokyo, Japan; Department of Neurological Surgery, Nippon Medical School, Tokyo, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Morita
authors.affiliation: Department of Clinical Neurosciences, University of Helsinki, Helsinki, Finland.
authors.forename: Seppo
authors.initials: S
authors.lastname: Juvela
authors.affiliation: Department of Neurosurgery, National Nagasaki Medical Center, Nagasaki, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yonekura
authors.affiliation: Division of Endovascular Neurosurgery, Tokyo Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ishibashi
authors.affiliation: Department of Epidemiology, University of Iowa, Iowa City, IA, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Torner
authors.affiliation: Department of Health Informatics, Kyoto University School of Public Health, Kyoto, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Nakayama
authors.affiliation: Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands.
authors.forename: Gabriël J E
authors.initials: GJ
authors.lastname: Rinkel
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, Netherlands; Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, Netherlands.
authors.forename: Ale
authors.initials: A
authors.lastname: Algra
mesh_terms: D017542:Aneurysm, Ruptured / Q000175:diagnosis* / Q000453:epidemiology; D015331:Cohort Studies; D006801:Humans; D002532:Intracranial Aneurysm / Q000175:diagnosis* / Q000453:epidemiology; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012720:Severity of Illness Index