title: The NASS lumbar spine outcome assessment instrument: Large sample assessment and sub-scale identification.
abstract: BACKGROUND
  Accurately assessing patient-reported pain and functional ability is essential to measuring quality of care.
  
  
  OBJECTIVE
  Evaluating the instruments used in assessing quality of care is often overlooked. The North American Spine Society Lumbar Spine Outcome Assessment (NASS-LS) instrument measures patient-reported pain and function in a combined scale. We evaluated the original instrument and assessed separate pain and function subscales based on a set of the items in the original instrument.
  
  
  METHODS
  Data were collected from seven spine clinics in the United States participating in the Spinal Surgery Consortium for Outcomes Research Project. Consenting patients were enrolled in the project and asked to complete the NASS instrument when arriving for a surgical consult.
  
  
  METHODS
  Data from 811 lumbar spine patients were used.
  
  
  METHODS
  Analyses were conducted on the original instrument to determine its internal consistency and to determine the structural existence of any underlying scales. Internal consistency of the original and new scales were assessed with Cronbach's coefficient alpha.
  
  
  RESULTS
  The original scale was found to be a useful measure of pain and functional ability. Important subscales of pain and functional ability were also identified allowing us to report more meaningful results.
  
  
  CONCLUSIONS
  The original instrument is useful for assessing low-back pain and function as a combined concept. The separate pain and function scales may prove useful assessing varying outcome levels and/or different decisions about subsequent follow-up care.
authors.affiliation: Department of Neurosurgery and Center for Health Services Research, Henry Ford Health System, Detroit, MI, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Morlock
authors.forename: D R
authors.initials: DR
authors.lastname: Nerenz