title: Derivation and validation of QStroke score for predicting risk of ischaemic stroke in primary care and comparison with other risk scores: a prospective open cohort study.
abstract: OBJECTIVE
  To develop and validate a risk algorithm (QStroke) to estimate risk of stroke or transient ischaemic attack in patients without prior stroke or transient ischaemic attack at baseline; to compare (a) QStroke with CHADS2 and CHA2DS2VASc scores in patients with atrial fibrillation and (b) the performance of QStroke with the Framingham stroke score in the full population free of stroke or transient ischaemic attack.
  
  
  METHODS
  Prospective open cohort study using routinely collected data from general practice during the study period 1 January 1998 to 1 August 2012.
  
  
  METHODS
  451 general practices in England and Wales contributing to the national QResearch database to develop the algorithm and 225 different QResearch practices to validate the algorithm.
  
  
  METHODS
  3.5 million patients aged 25-84 years with 24.8 million person years in the derivation cohort who experienced 77,578 stroke events. For the validation cohort, we identified 1.9 million patients aged 25-84 years with 12.7 million person years who experienced 38,404 stroke events. We excluded patients with a prior diagnosis of stroke or transient ischaemic attack and those prescribed oral anticoagulants at study entry.
  
  
  METHODS
  Incident diagnosis of stroke or transient ischaemic attack recorded in general practice records or linked death certificates during follow-up.
  
  
  METHODS
  Self assigned ethnicity, age, sex, smoking status, systolic blood pressure, ratio of total serum cholesterol to high density lipoprotein cholesterol concentrations, body mass index, family history of coronary heart disease in first degree relative under 60 years, Townsend deprivation score, treated hypertension, type 1 diabetes, type 2 diabetes, renal disease, rheumatoid arthritis, coronary heart disease, congestive cardiac failure, valvular heart disease, and atrial fibrillation
  
  
  RESULTS
  The QStroke algorithm explained 57% of the variation in women and 55% in men without a prior stroke. The D statistic for QStroke was 2.4 in women and 2.3 in men. QStroke had improved performance on all measures of discrimination and calibration compared with the Framingham score in patients without a prior stroke. Among patients with atrial fibrillation, levels of discrimination were lower, but QStroke had some improved performance on all measures of discrimination compared with CHADS2 and CHA2DS2VASc.
  
  
  CONCLUSIONS
  QStroke provides a valid measure of absolute stroke risk in the general population of patients free of stroke or transient ischaemic attack as shown by its performance in a separate validation cohort. QStroke also shows some improvement on current risk scoring methods, CHADS2 and CHA2DS2VASc, for the subset of patients with atrial fibrillation for whom anticoagulation may be required. Further research is needed to evaluate the cost effectiveness of using these algorithms in primary care.
authors: Division of Primary Care, University Park, Nottingham NG2 7RD, UK. Julia.hippisley-cox@nottingham.ac.uk
authors: Julia
authors: J
authors: Hippisley-Cox
authors: Carol
authors: C
authors: Coupland
authors: Peter
authors: P
authors: Brindle
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001172:Arthritis, Rheumatoid / Q000453:epidemiology; D001281:Atrial Fibrillation / Q000453:epidemiology; D001794:Blood Pressure; D015992:Body Mass Index; D002784:Cholesterol / Q000097:blood; D008076:Cholesterol, HDL / Q000097:blood; D003327:Coronary Disease / Q000453:epidemiology / Q000235:genetics; D003920:Diabetes Mellitus / Q000453:epidemiology; D005260:Female; D006333:Heart Failure / Q000453:epidemiology; D006349:Heart Valve Diseases / Q000453:epidemiology; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D015994:Incidence; D002546:Ischemic Attack, Transient / Q000453:epidemiology*; D007674:Kidney Diseases / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D011446:Prospective Studies; D044469:Racial Groups; D012044:Regression Analysis; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology; D020521:Stroke / Q000453:epidemiology*; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D008076:Cholesterol, HDL; D002784:Cholesterol
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