title: Floor and ceiling effects in the OHS: an analysis of the NHS PROMs data set.
abstract: OBJECTIVE
  The objective was to examine whether the Oxford Hip Score (OHS) demonstrated a floor or a ceiling effect when used to measure the outcome of hip replacement surgery in a large national cohort.
  
  
  METHODS
  Secondary database analysis of a national audit conducted in England and Wales on patient undergoing hip and knee arthroplasty in a secondary care setting.
  
  
  METHODS
  93 253 primary arthroplasty patients completed preoperative OHS questionnaires and 69 361 completed 6-month postoperative OHS questionnaires. The population had a mean age of 67.78 (range 14-100, SD 11.3) and 59% were female.
  Primary outcome measure was the Oxford Hip Score (OHS). Secondary outcome measures were the OHS-FCS and OHS-PCS. Floor and ceiling effects were considered present if >15% of patients achieved the worst score/floor effect (0/48) or best/ceiling effect (48/48) score.
  
  
  RESULTS
  Preoperatively, 0% of patients achieved the best score (48) and 0.1% achieved the worst score (0). Postoperatively, 0.1% patients achieved the worst score, but the percentage achieving the best score increased to 11.6%. Subgroup analyses demonstrated that patients between 50 and 59 years of age had the highest postoperative best score, at 15.3%. The highest postoperative OHS worst score percentage was in a group of patients who had a preoperative OHS above 41/48 at 28%. Furthermore, 22.6% of patients achieved the best postoperative OHS-PCS and 19.9% best postoperative OHS-FCS.
  
  
  CONCLUSIONS
  Based on NHS PROMS data the overall OHS does not exhibit a ceiling or floor effect and should continue to be used as a valid measure of patient-reported outcomes for patients undergoing total hip arthroplasty. However, subscale analysis does indicate some limitations in the OHS-PCS and OHS-FCS.
  
  
  BACKGROUND
  NDORMS. Introducing standardised and evidence-based thresholds for hip and knee replacement surgery. The Arthroplasty Candidacy Help Engine (ACHE tool). HTA Project 11/63/01.
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Lim
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: Kristina
authors.initials: K
authors.lastname: Harris
authors.affiliation: Department of Public Health, Oxford University, Oxford, UK.
authors.forename: Jill
authors.initials: J
authors.lastname: Dawson
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beard
authors.affiliation: Health Services Research Unit, Oxford University, Oxford, UK.
authors.forename: Ray
authors.initials: R
authors.lastname: Fitzpatrick
authors.affiliation: Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Price
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000706:statistics & numerical data*; D004739:England; D005260:Female; D006801:Humans; D008297:Male; D008485:Medical Audit; D008875:Middle Aged; D010147:Pain Measurement; D010149:Postoperative Pain / Q000503:physiopathology*; D063868:Patient Outcome Assessment; D012720:Severity of Illness Index; D013222:State Medicine / Q000706:statistics & numerical data; D011795:Surveys and Questionnaires; D014852:Wales
keywords: ORTHOPAEDIC & TRAUMA SURGERY