title: Psychometric characteristics of the Spanish version of instruments to measure neck pain disability.
abstract: BACKGROUND
  The NDI, COM and NPQ are evaluation instruments for disability due to NP. There was no Spanish version of NDI or COM for which psychometric characteristics were known. The objectives of this study were to translate and culturally adapt the Spanish version of the Neck Disability Index Questionnaire (NDI), and the Core Outcome Measure (COM), to validate its use in Spanish speaking patients with non-specific neck pain (NP), and to compare their psychometric characteristics with those of the Spanish version of the Northwick Pain Questionnaire (NPQ).
  
  
  METHODS
  Translation/re-translation of the English versions of the NDI and the COM was done blindly and independently by a multidisciplinary team. The study was done in 9 primary care Centers and 12 specialty services from 9 regions in Spain, with 221 acute, subacute and chronic patients who visited their physician for NP: 54 in the pilot phase and 167 in the validation phase. Neck pain (VAS), referred pain (VAS), disability (NDI, COM and NPQ), catastrophizing (CSQ) and quality of life (SF-12) were measured on their first visit and 14 days later. Patients' self-assessment was used as the external criterion for pain and disability. In the pilot phase, patients' understanding of each item in the NDI and COM was assessed, and on day 1 test-retest reliability was estimated by giving a second NDI and COM in which the name of the questionnaires and the order of the items had been changed.
  
  
  RESULTS
  Comprehensibility of NDI and COM were good. Minutes needed to fill out the questionnaires [median, (P25, P75)]: NDI. 4 (2.2, 10.0), COM: 2.1 (1.0, 4.9). Reliability: [ICC, (95%CI)]: NDI: 0.88 (0.80, 0.93). COM: 0.85 (0.75,0.91). Sensitivity to change: Effect size for patients having worsened, not changed and improved between days 1 and 15, according to the external criterion for disability: NDI: -0.24, 0.15, 0.66; NPQ: -0.14, 0.06, 0.67; COM: 0.05, 0.19, 0.92.
  
  
  RESULTS
  Results of NDI, NPQ and COM were consistent with the external criterion for disability, whereas only those from NDI were consistent with the one for pain. Correlations with VAS, CSQ and SF-12 were similar for NDI and NPQ (absolute values between 0.36 and 0.50 on day 1, between 0.38 and 0.70 on day 15), and slightly lower for COM (between 0.36 and 0.48 on day 1, and between 0.33 and 0.61 on day 15). Correlation between NDI and NPQ: r = 0.84 on day 1, r = 0.91 on day 15. Correlation between COM and NPQ: r = 0.63 on day 1, r = 0.71 on day 15.
  
  
  CONCLUSIONS
  Although most psychometric characteristics of NDI, NPQ and COM are similar, those from the latter one are worse and its use may lead to patients' evolution seeming more positive than it actually is. NDI seems to be the best instrument for measuring NP-related disability, since its results are the most consistent with patient's assessment of their own clinical status and evolution. It takes two more minutes to answer the NDI than to answer the COM, but it can be reliably filled out by the patient without assistance.
  
  
  BACKGROUND
  Clinical Trials Register NCT00349544.
authors.affiliation: Departamento Científico, Fundación Kovacs, Palma de Mallorca, Spain. kovacs@kovacs.org
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Kovacs
authors.forename: Joan
authors.initials: J
authors.lastname: Bagó
authors.forename: Ana
authors.initials: A
authors.lastname: Royuela
authors.forename: Jesús
authors.initials: J
authors.lastname: Seco
authors.forename: Sergio
authors.initials: S
authors.lastname: Giménez
authors.forename: Alfonso
authors.initials: A
authors.lastname: Muriel
authors.forename: Víctor
authors.initials: V
authors.lastname: Abraira
authors.forename: José Luis
authors.initials: JL
authors.lastname: Martín
authors.forename: José Luis
authors.initials: JL
authors.lastname: Peña
authors.forename: Mario
authors.initials: M
authors.lastname: Gestoso
authors.forename: Nicole
authors.initials: N
authors.lastname: Mufraggi
authors.forename: Montserrat
authors.initials: M
authors.lastname: Núñez
authors.forename: Josep
authors.initials: J
authors.lastname: Corcoll
authors.forename: Ignacio
authors.initials: I
authors.lastname: Gómez-Ochoa
authors.forename: Ma José
authors.initials: MJ
authors.lastname: Ramírez
authors.forename: Eva
authors.initials: E
authors.lastname: Calvo
authors.forename: Ma Dolores
authors.initials: MD
authors.lastname: Castillo
authors.forename: David
authors.initials: D
authors.lastname: Martí
authors.forename: Salvador
authors.initials: S
authors.lastname: Fuster
authors.forename: Carmen
authors.initials: C
authors.lastname: Fernández
authors.forename: Nuria
authors.initials: N
authors.lastname: Gimeno
authors.forename: Alejandro
authors.initials: A
authors.lastname: Carballo
authors.forename: Alvaro
authors.initials: A
authors.lastname: Milán
authors.forename: Dolores
authors.initials: D
authors.lastname: Vázquez
authors.forename: Montserrat
authors.initials: M
authors.lastname: Cañellas
authors.forename: Ricardo
authors.initials: R
authors.lastname: Blanco
authors.forename: Pilar
authors.initials: P
authors.lastname: Brieva
authors.forename: Ma Trinidad
authors.initials: MT
authors.lastname: Rueda
authors.forename: Luis
authors.initials: L
authors.lastname: Alvarez
authors.forename: María Teresa Gil
authors.initials: MT
authors.lastname: Del Real
authors.forename: Joaquín
authors.initials: J
authors.lastname: Ayerbe
authors.forename: Luis
authors.initials: L
authors.lastname: González
authors.forename: Leovigildo
authors.initials: L
authors.lastname: Ginel
authors.forename: Mariano
authors.initials: M
authors.lastname: Ortega
authors.forename: Miryam
authors.initials: M
authors.lastname: Bernal
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Bolado
authors.forename: Anna
authors.initials: A
authors.lastname: Vidal
authors.forename: Ana
authors.initials: A
authors.lastname: Ausín
authors.forename: Domingo
authors.initials: D
authors.lastname: Ramón
authors.forename: María Antonia
authors.initials: MA
authors.lastname: Mir
authors.forename: Miquel
authors.initials: M
authors.lastname: Tomás
authors.forename: Javier
authors.initials: J
authors.lastname: Zamora
authors.forename: Alejandra
authors.initials: A
authors.lastname: Cano
mesh_terms: D000328:Adult; D000368:Aged; D003466:Cultural Characteristics; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019547:Neck Pain / Q000175:diagnosis*; D010147:Pain Measurement / Q000379:methods*; D011594:Psychometrics; D011788:Quality of Life; D015203:Reproducibility of Results; D013030:Spain; D011795:Surveys and Questionnaires; D014175:Translating