title: Validation of a mobility item bank for older patients in primary care.
abstract: BACKGROUND
  To develop and validate an item bank to measure mobility in older people in primary care and to analyse differential item functioning (DIF) and differential bundle functioning (DBF) by sex.
  
  
  METHODS
  A pool of 48 mobility items was administered by interview to 593 older people attending primary health care practices. The pool contained four domains based on the International Classification of Functioning: changing and maintaining body position, carrying, lifting and pushing, walking and going up and down stairs.
  
  
  RESULTS
  The Late Life Mobility item bank consisted of 35 items, and measured with a reliability of 0.90 or more across the full spectrum of mobility, except at the higher end of better functioning. No evidence was found of non-uniform DIF but uniform DIF was observed, mainly for items in the changing and maintaining body position and carrying, lifting and pushing domains. The walking domain did not display DBF, but the other three domains did, principally the carrying, lifting and pushing items.
  
  
  CONCLUSIONS
  During the design and validation of an item bank to measure mobility in older people, we found that strength (carrying, lifting and pushing) items formed a secondary dimension that produced DBF. More research is needed to determine how best to include strength items in a mobility measure, or whether it would be more appropriate to design separate measures for each construct.
authors.affiliation: Department of Nursing, University of Alicante, San Vicente del Raspeig, Alicante, Spain. julio.cabrero@ua.es
authors.forename: Julio
authors.initials: J
authors.lastname: Cabrero-García
authors.forename: Juan Diego
authors.initials: JD
authors.lastname: Ramos-Pichardo
authors.forename: Carmen Luz
authors.initials: CL
authors.lastname: Muñoz-Mendoza
authors.forename: María José
authors.initials: MJ
authors.lastname: Cabañero-Martínez
authors.forename: Lorena
authors.initials: L
authors.lastname: González-Llopis
authors.forename: Abilio
authors.initials: A
authors.lastname: Reig-Ferrer
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D016330:Frail Elderly; D006801:Humans; D007802:Language; D008297:Male; D015233:Models, Statistical; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology; D011320:Primary Health Care; D036301:Qualitative Research; D012737:Sex Factors; D011795:Surveys and Questionnaires / Q000592:standards*; D016138:Walking / Q000502:physiology; D014891:Weight Lifting / Q000502:physiology