Associations between heat pain perception and pain severity among patients with chronic pain.

OBJECTIVE

The primary aim of this study was to investigate the associations between standardized values of thermal sensory perception and standardized scores of clinical pain among a heterogeneous cohort of adults with chronic pain that included individuals receiving chronic opioid therapy.

DESIGN

The study used a prospective design.

SETTING

The study was set in a multidisciplinary pain rehabilitation center at a tertiary medical center.

PATIENTS

The cohort included 163 patients (female 58%) who met inclusion criteria, and were admitted from March 2007 to June 2008.

INTERVENTION

Using a validated quantitative sensory test method of levels, standardized values of heat pain (HP) perception and cooling detection threshold were obtained 1day following admission.

OUTCOME MEASURES

Standardized scores of clinical pain were obtained at admission using the pain severity subscale of the Multidimensional Pain Inventory.

RESULTS

At admission, 109 (67%) patients were using opioids, and the mean morphine equivalent dose was 192mg/day. The mean pain duration was 10.5years, and the two most frequent diagnoses were low back pain (29%) and headache (12%). A significant negative correlation was found between pain severity and HP threshold (r=-0.170, P=0.030), where lower values of HP threshold correlated with greater scores of pain severity. Post hoc linear regression analysis showed the association between HP threshold and pain severity retained statistical significance (P=0.039) after adjusting for opioid dose, pain duration and pain diagnosis.

CONCLUSION

The use of standardized values of HP perception and clinical pain may be key methodological approaches for investigating the clinical correlates of HP perception among heterogeneous populations of adults with chronic pain.