title: Scottish Intracranial Vascular Malformation Study (SIVMS): evaluation of methods, ICD-10 coding, and potential sources of bias in a prospective, population-based cohort.
abstract: OBJECTIVE
  The rarity of intracranial vascular malformations (IVMs) and the infrequency of their outcomes make large, prolonged cohort studies the best means to evaluate their frequency and prognosis.
  
  
  METHODS
  The Scottish Intracranial Vascular Malformation Study (SIVMS) is a prototype prospective, population-based study of adults resident in Scotland and diagnosed for the first time with an IVM after January 1, 1999. We evaluated the design of SIVMS using 2 complete years of data for adults with arteriovenous malformations (AVMs) of the brain.
  
  
  RESULTS
  A collaborative network of clinicians, radiologists, and pathologists, combined with coding of hospital discharge data and death certificates, recruited a cohort distributed in proportion to the Scottish population. Coding (with International Classification of Diseases, 10th Revision [ICD-10] codes Q28.2 and I60.8) had a sensitivity of 72% (95% CI, 61% to 80%) and a positive predictive value of 46% (95% CI, 38% to 55%) for detecting incident brain AVMs. Adults who were detected by coding alone were significantly (P<0.05) younger, more likely to present with hemorrhage, more frequently investigated with catheter angiography, and more likely to be treated. Adults recruited from tertiary referral centers were significantly more likely to be investigated with catheter angiography and to be treated. Using catheter angiography as a diagnostic requirement for brain AVMs significantly biases the cohort toward younger adults presenting with hemorrhage and receiving treatment.
  
  
  CONCLUSIONS
  Population-based studies of IVM frequency and prognosis should use multiple overlapping sources of case ascertainment, and such studies of brain AVMs should not require catheter angiography to be the diagnostic standard.
authors.affiliation: Department of Clinical Neurosciences, Western General Hospital, Edinburgh, Scotland. Rustam.Al-Shahi@ed.ac.uk
authors.forename: Rustam
authors.initials: R
authors.lastname: Al-Shahi
authors.forename: Jo J
authors.initials: JJ
authors.lastname: Bhattacharya
authors.forename: David G
authors.initials: DG
authors.lastname: Currie
authors.forename: Vakis
authors.initials: V
authors.lastname: Papanastassiou
authors.forename: Vaughn
authors.initials: V
authors.lastname: Ritchie
authors.forename: Richard C
authors.initials: RC
authors.lastname: Roberts
authors.forename: Robin J
authors.initials: RJ
authors.lastname: Sellar
authors.forename: Charles P
authors.initials: CP
authors.lastname: Warlow
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002533:Cerebral Angiography / Q000706:statistics & numerical data; D002543:Cerebral Hemorrhage / Q000209:etiology; D015331:Cohort Studies; D003625:Data Collection; D003644:Death Certificates; D004827:Epilepsy / Q000209:etiology; D005260:Female; D006801:Humans; D038801:International Classification of Diseases; D002538:Intracranial Arteriovenous Malformations / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000453:epidemiology* / Q000628:therapy; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010351:Patient Discharge / Q000706:statistics & numerical data; D018579:Patient Selection; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012606:Scotland / Q000453:epidemiology; D015983:Selection Bias; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed