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Cluster Analysis of an International Pressure Pain Threshold Database Identifies 4 Meaningful Subgroups of Adults With Mechanical Neck Pain

Walton, David M. PT, PhD; Kwok, Timothy S.H. BSc; Mehta, Swati PhD(c); Loh, Eldon MD; Smith, Ashley PT, PhD; Elliott, James PT, PhD; Kamper, Steven J. PT, PhD; Kasch, Helge PhD; Sterling, Michele PT, PhD

doi: 10.1097/AJP.0000000000000421
Original Articles

Objective: To determine pressure pain detection threshold (PPDT) related phenotypes of individuals with mechanical neck pain that may be identifiable in clinical practice.

Methods: This report describes a secondary analysis of 5 independent, international mechanical neck pain databases of PPDT values taken at both a local and distal region (total N=1176). Minor systematic differences in mean PPDT values across cohorts necessitated z-transformation before analysis, and each cohort was split into male and female sexes. Latent profile analysis (LPA) using the k-means approach was undertaken to identify the most parsimonious set of PPDT-based phenotypes that were both statistically and clinically meaningful.

Results: LPA revealed 4 distinct clusters named according to PPDT levels at the local and distal zones: low-low PPDT (67%), mod-mod (25%), mod-high (4%), and high-high (4%). Secondary predictor variables were evaluated for intracluster and cross-cluster significance. Low-low cluster was most affected, as indicated by pain intensity, disability, and catastrophization scores all significantly above the cohort-specific and sex-specific mean, and active range of motion scores significantly below the mean.

Discussion: The results suggest that there are a large proportion of people with neck pain that present with signs indicating dysfunction beyond the local tissues. Ongoing exploration of these presentations may lead to more informed management and improved outcomes.

*Faculty of Health Sciences

Schulich School of Medicine and Dentistry, Western University, London, ON, Canada

§Feinberg School of Medicine, Northwestern University, Chicago, IL

Menzies Health Institute, Griffith University, Southport, Qld

George Institute for Global Health, Sydney, NSW, Australia

Department of Neurology, Aarhus University, Aarhus, Denmark

D.M.W.: study design, acquisition of data, data analysis and interpretation, drafting of article, final approval. T.S.H.K.: data analysis and interpretation, final approval. S.M.: data analysis and interpretation, final approval. E.L.: critical revisions, data provision, final approval. A.S.: acquisition of data, critical revisions, final approval. J.E.: acquisition of data, critical revisions, final approval. S.J.K.: acquisition of data, critical revisions, final approval. H.K.: acquisition of data, critical revisions, final approval. M.S.: acquisition of data, critical revisions, final approval.

Supported by The Canadian Institutes of Health Research (Canada), The National Institutes of Health (USA), The National Health and Medical Research Council (Australia). J.E. is a board member of the Journal of Orthopedic and Sports Physical Therapy and Spine, and holds 35% ownership in Pain ID LLC. D.M.W. is a board member of Manual Therapy and the Journal of Orthopedic and Sports Physical Therapy and is owner of David Walton Rehabilitation Education, Consultation and Research. The remaining authors declare no conflict of interest.

Reprints: David M. Walton, PT, PhD, Faculty of Health Sciences, Western University Canada, Rm. EC1443, School of Physical Therapy, 1201 Western Rd., London, ON, Canada N6G 1H1 (e-mail: dwalton5@uwo.ca).

Received December 17, 2015

Received in revised form October 25, 2016

Accepted July 16, 2016

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