Subgroups based on thermal and pressure pain thresholds in women with chronic whiplash display differences in clinical presentation – an explorative study

Björn Börsbo,^1,2 Gunilla M Liedberg,³ Mia Wallin,^1,3 Björn Gerdle<sup>1,4

1</sup>Department of Medicine and Health Sciences, University of Linköping, Linköping, Sweden; ²Clinical Department of Rehabilitation Medicine, County Hospital Ryhov, Jönköping, Sweden; ³Department of Social and Welfare Studies, University of Linköping, Norrköping, Sweden; ⁴Pain and Rehabilitation Centre, UHL, Östergötland County Council, Linköping, Sweden

Purpose: To investigate the presence of subgroups in chronic whiplash-associated disorders (WAD) based on pain thresholds for pressure (PPT), cold (CPT), and heat (HPT) and to compare these subgroups with respect to symptomatology, disability, and health aspects.
Methods: Two groups of female subjects – patients with chronic WAD (n = 28) and healthy controls (CON; n = 29) – were investigated. Quantitative sensory testing (QST) for thermal thresholds and algometry for PPT at four sites in the body (over the trapezius and tibialis anterior bilaterally) were determined. Habitual pain intensities, psychological strain, disability, and health aspects were registered using a questionnaire.
Results: A cluster analysis based on PPT, CPT, and HPT identified two subgroups of chronic WAD: one sensitive subgroup (s-WAD; n = 21), and one less sensitive subgroup (ls-WAD; n = 6). S-WAD displayed widespread hyperalgesia, whereas ls-WAD had localized hyperalgesia in the neck area, with tendencies to supernormal values in remote areas of the body. Generally, s-WAD had a significantly worse situation than the CON with respect to symptomatology, disability, and health aspects. The ls-WAD group was intermediary between s-WAD and CON in these aspects.
Conclusion: Different explanations, eg, severity of the pain condition per se, etiological factors, and pre-trauma differences in pain sensitivity, may exist for the differences in pain thresholds between the two subgroups. Future research should investigate the role of pain thresholds in the chronic stage to determine the efficacy of treatment interventions.

Keywords: cold pain threshold, pain, pressure pain threshold, heat pain threshold, subgroup, whiplash, WAD