title: Adaptation of clinical prediction models for application in local settings.
abstract: When planning to use a validated prediction model in new patients, adequate performance is not guaranteed. For example, changes in clinical practice over time or a different case mix than the original validation population may result in inaccurate risk predictions.
  
  
  
  To demonstrate how clinical information can direct updating a prediction model and development of a strategy for handling missing predictor values in clinical practice.
  
  
  
  A previously derived and validated prediction model for postoperative nausea and vomiting was updated using a data set of 1847 patients. The update consisted of 1) changing the definition of an existing predictor, 2) reestimating the regression coefficient of a predictor, and 3) adding a new predictor to the model. The updated model was then validated in a new series of 3822 patients. Furthermore, several imputation models were considered to handle real-time missing values, so that possible missing predictor values could be anticipated during actual model use.
  
  
  
  Differences in clinical practice between our local population and the original derivation population guided the update strategy of the prediction model. The predictive accuracy of the updated model was better (c statistic, 0.68; calibration slope, 1.0) than the original model (c statistic, 0.62; calibration slope, 0.57). Inclusion of logistical variables in the imputation models, besides observed patient characteristics, contributed to a strategy to deal with missing predictor values at the time of risk calculation.
  
  
  
  Extensive knowledge of local, clinical processes provides crucial information to guide the process of adapting a prediction model to new clinical practices.
authors.affiliation: Division of Anesthesiology, Intensive Care and Emergency Medicine (THK, WAVK, LVW, CJK, KGMM)
authors.forename: Teus H
authors.initials: TH
authors.lastname: Kappen
authors.affiliation: Julius Center for Health Sciences and Primary Care (YV, KGMM), University Medical Center Utrecht, Utrecht, the Netherlands
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Vergouwe
authors.affiliation: Division of Anesthesiology, Intensive Care and Emergency Medicine (THK, WAVK, LVW, CJK, KGMM)
authors.forename: Wilton A
authors.initials: WA
authors.lastname: van Klei
authors.affiliation: Division of Anesthesiology, Intensive Care and Emergency Medicine (THK, WAVK, LVW, CJK, KGMM)
authors.forename: Leo
authors.initials: L
authors.lastname: van Wolfswinkel
authors.affiliation: Division of Anesthesiology, Intensive Care and Emergency Medicine (THK, WAVK, LVW, CJK, KGMM)
authors.forename: Cor J
authors.initials: CJ
authors.lastname: Kalkman
authors.affiliation: Division of Anesthesiology, Intensive Care and Emergency Medicine (THK, WAVK, LVW, CJK, KGMM)|Julius Center for Health Sciences and Primary Care (YV, KGMM), University Medical Center Utrecht, Utrecht, the Netherlands
authors.forename: Karel G M
authors.initials: KG
authors.lastname: Moons
mesh_terms: D016001:Confidence Intervals; D003657:Decision Making; D020000:Decision Support Systems, Clinical / Q000295:instrumentation*; D005260:Female; D005843:Geography; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017146:Models, Organizational; D019982:Organizational Case Studies; D011237:Predictive Value of Tests; D012372:ROC Curve; D018570:Risk Assessment / Q000379:methods