title: The mechanical and inflammatory low back pain (MIL) index: development and validation.
abstract: BACKGROUND
  The purpose of this study was the development of a valid and reliable "Mechanical and Inflammatory Low Back Pain Index" (MIL) for assessment of non-specific low back pain (NSLBP). This 7-item tool assists practitioners in determining whether symptoms are predominantly mechanical or inflammatory.
  
  
  METHODS
  Participants (n = 170, 96 females, age = 38 ± 14 years-old) with NSLP were referred to two Spanish physiotherapy clinics and completed the MIL and the following measures: the Roland Morris Questionnaire (RMQ), SF-12 and "Backache Index" (BAI) physical assessment test. For test-retest reliability, 37 consecutive patients were assessed at baseline and three days later during a non-treatment period. Face and content validity, practical characteristics, factor analysis, internal consistency, discriminant validity and convergent validity were assessed from the full sample.
  
  
  RESULTS
  A total of 27 potential items that had been identified for inclusion were subsequently reduced to 11 by an expert panel. Four items were then removed due to cross-loading under confirmatory factor analysis where a two-factor model yielded a good fit to the data (χ2 = 14.80, df = 13, p = 0.37, CFI = 0.98, and RMSEA = 0.029). The internal consistency was moderate (α = 0.68 for MLBP; 0.72 for ILBP), test-retest reliability high (ICC = 0.91; 95%CI = 0.88-0.93) and discriminant validity good for either MLBP (AUC = 0.74) and ILBP (AUC = 0.92). Convergent validity was demonstrated through similar but weak correlations between the ILBP and both the RMQ and BAI (r = 0.34, p < 0.001) and the MLBP and BAI (r = 0.38, p < 0.001).
  
  
  CONCLUSIONS
  The MIL is a valid and reliable clinical tool for patients with NSLBP that discriminates between mechanical and inflammatory LBP.
authors.affiliation: School Clinical Science at Queensland University of Technology, Brisbane, Australia. acuesta.var@gmail.com.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cuesta-Vargas
authors.forename: Andre
authors.initials: A
authors.lastname: Farasyn
authors.forename: Charles Philip
authors.initials: CP
authors.lastname: Gabel
authors.forename: Juan V
authors.initials: JV
authors.lastname: Luciano
mesh_terms: D000328:Adult; D019540:Area Under Curve; D005260:Female; D006801:Humans; D007249:Inflammation / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D017116:Low Back Pain / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010147:Pain Measurement / Q000379:methods*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011594:Psychometrics; D012372:ROC Curve; D015203:Reproducibility of Results; D012307:Risk Factors; D012720:Severity of Illness Index; D013030:Spain; D011795:Surveys and Questionnaires; D055815:Young Adult