title: Patients with low back pain had distinct clinical course patterns that were typically neither complete recovery nor constant pain. A latent class analysis of longitudinal data.
abstract: BACKGROUND
  The clinical presentation and outcome of patients with nonspecific low back pain (LBP) are very heterogeneous and may be better understood by the recognition of reproducible subgroups. One approach to subgrouping is the identification of clinical course patterns (trajectories). However, it has been unclear how dependent these trajectories are on the analytical model used and the pain characteristics included.
  
  
  OBJECTIVE
  To identify LBP trajectories using LBP intensity and frequency measured once a week over 1 year and compare the results obtained using different analytical approaches.
  
  
  METHODS
  A prospective observational cohort study.
  
  
  METHODS
  Patients presenting with nonspecific LBP to general practitioners and chiropractors.
  
  
  METHODS
  Weekly self-report of LBP intensity (0-10) and the number of LBP days measured by short message service cell phone questions over a 1-year follow-up period.
  
  
  METHODS
  Latent class analysis was used to identify the trajectories of LBP and 12 different analytical models were compared. The study was a component of a broader study funded by an unrestricted grant from the Danish Chiropractors' Foundation (USD 370,000).
  
  
  RESULTS
  The study included 1,082 patients. The 12 models resulted in 5 to 12 subgroups, with a number of trajectories stable across models that differed on pain intensity, number of LBP days, and shape of trajectory.
  
  
  CONCLUSIONS
  The clinical course of LBP is complex. Most primary care patients do not become pain-free within a year, but only a small proportion reports constant severe pain. Some distinct patterns exist which were identified independently of the way the outcome was modeled. These patterns would not be revealed by using the simple summary measures traditionally applied in LBP research or when describing a patient's pain history only in terms of duration. The appropriate number of subgroups will depend on the intended purpose of subgrouping.
authors: The Nordic Institute of Chiropractic and Clinical Biomechanics, Campusvej 55, 5230 Odense M, Denmark; Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark. Electronic address: a.kongsted@nikkb.dk.
authors: Alice
authors: A
authors: Kongsted
authors: Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
authors: Peter
authors: P
authors: Kent
authors: The Nordic Institute of Chiropractic and Clinical Biomechanics, Campusvej 55, 5230 Odense M, Denmark; Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
authors: Lise
authors: L
authors: Hestbaek
authors: The Nordic Institute of Chiropractic and Clinical Biomechanics, Campusvej 55, 5230 Odense M, Denmark; Working Group Clinical Epidemiology, Institute of Medical Biometry and Medical Informatics, University of Freiburg, Stefan-Meier-Strasse 26, Freiburg, Germany.
authors: Werner
authors: W
authors: Vach
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000175:diagnosis*; D008297:Male; D017063:Outcome Assessment, Health Care; D010147:Pain Measurement; D011446:Prospective Studies
keywords: Latent class analysis; Low back pain; Musculoskeletal pain; Primary health care; Prognosis; Trajectory