title: [Clinical prediction rules: a reader's guide].
abstract: BACKGROUND
  Clinical prediction rules or scores are instruments that allow to quantify the respective contributions of medical history, clinical examination and laboratory tests to a diagnosis or a prognosis in a given patient.
  
  
  BACKGROUND
  The development of clinical prediction rules requires three steps: 1) derivation of the rule from a population with known clinical characteristics and diagnosis or prognosis; 2) validation of the rule in a population distinct from the derivation sample; and 3) evaluation of the impact of the rule on clinician behavior and patient outcomes.
  
  
  CONCLUSIONS
  This paper provides a guide for the critical appraisal of a prediction rule illustrated by two clinical scores for the assessment of the clinical probability of pulmonary embolism.
  
  
  CONCLUSIONS
  Clinical prediction rules or scores have become indispensable components of the clinician's toolbox.
authors.affiliation: Clinique de Médecine 1, Département de Médecine, Hôpitaux Universitaires de Genève, Suisse. Arnaud.perrier@medecine.unige.ch
authors.forename: A
authors.initials: A
authors.lastname: Perrier
authors.forename: T
authors.initials: T
authors.lastname: Perneger
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001784:Blood Gas Analysis; D006469:Hemoptysis / Q000209:etiology; D006801:Humans; D007103:Immobilization / Q000009:adverse effects; D008487:Medical History Taking / Q000592:standards*; D008875:Middle Aged; D015233:Models, Statistical; D009369:Neoplasms / Q000150:complications; D010808:Physical Examination / Q000592:standards*; D017410:Practice Guidelines as Topic; D011237:Predictive Value of Tests; D011336:Probability; D011379:Prognosis; D001261:Pulmonary Atelectasis / Q000150:complications; D011655:Pulmonary Embolism / Q000097:blood / Q000175:diagnosis / Q000209:etiology*; D012008:Recurrence; D018570:Risk Assessment / Q000379:methods / Q000592:standards*; D012307:Risk Factors; D012720:Severity of Illness Index; D013610:Tachycardia / Q000150:complications