title: A new responder criterion (relative effect per patient (REPP) > 0.2) externally validated in a large total hip replacement multicenter cohort (EUROHIP).
abstract: OBJECTIVE
  To validate a new method to identify responders (relative effect per patient (REPP) >0.2) using the OMERACT-OARSI criteria as gold standard in a large multicentre sample.
  
  
  METHODS
  The REPP ([score before - after treatment]/score before treatment) was calculated for 845 patients of a large multicenter European cohort study for THR. The patients with a REPP >0.2 were defined as responders. The responder rate was compared to the gold standard (OMERACT-OARSI criteria) using receiver operator characteristic (ROC) curve analysis for sensitivity, specificity and percentage of appropriately classified patients.
  
  
  RESULTS
  With the criterion REPP>0.2 85.4% of the patients were classified as responders, applying the OARSI-OMERACT criteria 85.7%. The new method had 98.8% sensitivity, 94.2% specificity and 98.1% of the patients were correctly classified compared to the gold standard.
  
  
  CONCLUSIONS
  The external validation showed a high sensitivity and also specificity of a new criterion to identify a responder compared to the gold standard method. It is simple and has no uncertainties due to a single classification criterion.
authors.affiliation: Department of Orthopaedics, Stadtspital Triemli, Birmendsdorferstr. 497, CH-8063 Zurich, Switzerland. Electronic address: joerg.huber2@triemli.zuerich.ch.
authors.forename: J
authors.initials: J
authors.lastname: Huber
authors.affiliation: Institute for Mathematical Statistics, University of Bern, Sidlerstr. 5, CH-3012 Bern, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Hüsler
authors.affiliation: Peninsula College of Medicine and Dentistry, C420 Portland Square, University of Plymouth Campus, Drake Circus, Plymouth PL4 8 AA, UK.
authors.forename: P
authors.initials: P
authors.lastname: Dieppe
authors.affiliation: Department of Orthopaedics, Gustav Carus University of Dresden, Fetscherstr. 76, D-01307 Dresden, Germany.
authors.forename: K P
authors.initials: KP
authors.lastname: Günther
authors.affiliation: Centre of Musculosceletal Surgery, Charité, University of Berlin, Charitéplatz 1, D-10117 Berlin, Germany; Department of Orthopaedics, Traumatology and Sports Medicine, Medical Park Berlin Humboldtmühle, An der Mühle 2-9, D-13507 Berlin, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Dreinhöfer
authors.affiliation: Botnar Research Centre, Institute of Musculosceletal Sciences, Nuffield Department of Orthopaedics, Rheumatology and Musculosceletal Sciences, University of Oxford, Windmill Road, Headington, OX3 7LD, UK.
authors.forename: A
authors.initials: A
authors.lastname: Judge
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000601:surgery*; D010147:Pain Measurement / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D016896:Treatment Outcome
keywords: EUROHIP; OMERACT-OARSI; Outcome; REPP; Responder; THR