"Convergent validity of the central sensitization inventory and experimental testing of pain sensitivity".

OBJECTIVES: The aim of the current study was to examine the convergent validity of the Central Sensitization Inventory by quantifying the correlation with experimental measures of pain sensitivity and self-reported psycho-social questionnaires, in a low back pain population. METHODS: All participants were recruited from an outpatient hospital spine care clinic (Spine Centre of Southern Denmark). Participants underwent a standardized experimental pain test protocol and completed the Central Sensitization Inventory (CSI) along with additional self-reported questionnaires to assess psycho-social constructs across different domains. The association between the CSI, experimental pain measures and other self-reported psycho-social questionnaires were analyzed using correlation and contingency tests. ROC-curve analysis was used to determine sensitivity and specificity for CSI. RESULTS: One hundred sixty-eight (168) participants were included. The CSI was weakly correlated with nine out of 20 variables in the experimental pain test protocol (rho range -0.37 to 0.22). The CSI was more closely correlated with psycho-social factors such as work ability, disability, and symptoms of exhaustion disorder. ROC-analysis identified an optimal cut-point of 44 on CSI (Sn=39.1% Sp=87.4%). The CSI had an area under the ROC curve of 0.656. Fisher's exact test demonstrated a statistically significant association between participants scoring ≥40 on CSI and participants categorized as sensitized by experimental pain tests (p-value=0.03). CONCLUSIONS: Our findings are consistent with previous studies, indicating that the CSI is related to psycho-social constructs. However, the convergent validity with experimental pain measures is small and probably not clinically meaningful.

The inhibitory effect of conditioned pain modulation on temporal summation in low-back pain patients.

OBJECTIVES: The literature on conditioned pain modulation (CPM) is inconclusive in relation to low-back pain and it is unclear how CPM affects temporal summation as a proxy of central pain integration. The aim of this study was to examine whether the CPM effect would be different on pain induced by temporal summation than single stimuli in a group of low back pain patients. METHODS: A total of 149 low-back pain patients were included. CPM was examined using single, repeated and temporal summation (repeated-single difference) of mechanical pressure pain as test stimuli at an individualized, fixed supra-pain-threshold force, before and after 2 min of cold pressor test (0-2 degrees Celsius). Participants were categorized as CPM responders or non-responders according to three different criteria: simple (any pain inhibition), strict (pain inhibition of more than 10VAS) and reversed (pain inhibition or facilitation of less than 10VAS). Clinical data on back pain was collected for correlation and descriptive purposes. RESULTS: Significant modulation was observed for all three test stimuli. Effects sizes were comparable in relative terms, but repeated pressure pain modulation was greater in absolute terms. No correlations to clinical data were observed, for any measure. CONCLUSIONS: The current data suggests that repeated pressure pain may be better suited as the CPM test stimuli, than single pressure pain and temporal summation of pressure pain, as the CPM effect in absolute terms was greater. Employing temporal summation as the test stimulus in a CPM paradigm may be more sensitive than a single test stimulus.