Somatosensory nociceptive characteristics differentiate subgroups in people with chronic low back pain

The aims of this study were to investigate the existence of subgroups in a cohort with chronic low back pain (n=294) based upon results of multimodal sensory testing, and profile subgroups on demographic, psychological, lifestyle, and general health factors. Bedside (two-point discrimination; brush/vibration/pinprick perception; temporal summation on repeated monofilament stimulation) and laboratory (mechanical detection threshold; pressure/heat/cold pain thresholds; conditioned pain modulation) sensory testing were examined at wrist and lumbar sites. Data were entered into principal component analysis, and five component scores entered into latent class analysis. Three clusters, with different sensory characteristics, were derived. Cluster 1 (31.9%) was characterised by average to high temperature and pressure pain sensitivity. Cluster 2 (52.0%) was characterised by average to high pressure pain sensitivity. Cluster 3 (16.0%) was characterised by low temperature and pressure pain sensitivity. Temporal summation happened with significantly greater frequency in Cluster 1. Subgroups were profiled on pain intensity, disability, depression, anxiety, stress, life-events, fear-avoidance, catastrophizing, perception of body schema relating to the back region, comorbidities, body mass index, multiple pain sites, sleep and activity levels. Clusters 1 and 2 had a significantly higher proportion of female participants, and higher depression and sleep disturbance scores than Cluster 3. The proportion of participants undertaking <300 minutes/week of moderate activity was significantly greater in Cluster 1 than Clusters 2 and 3. Low back pain, therefore, does not seem to be homogeneous. Pain mechanisms relating to presentations of each subgroup were postulated. Future research might examine prognoses and interventions tailored towards these subgroups.