Background/Purpose: Fibromyalgia (FM) is a common chronic pain condition for which acupuncture treatment is increasingly utilized. However, there is no universally accepted measure to predict which specific patient may benefit from acupuncture. Our previous work showed that experimental pressure pain sensitivity can differentially predict responsiveness to active versus sham acupuncture therapy in FM. Here, we attempt to replicate this result in a significantly larger FM cohort and explore additional benefit of patient expectations in predicting pain relief following acupuncture.

Methods: A single center, single-blind, sham-controlled, randomized non-crossover longitudinal trial was approved by the local Institutional Review Board. Seventy-six subjects with FM were assigned to electroacupuncture (EA) or a placebo control, mock laser acupuncture (ML), treatment for 8 treatments given twice per week. Prior to treatment pain sensitivity was assessed by applying an inflatable blood-pressure cuff to the left calf. A tonic 6-minute pressure was applied at a pre-determined pain rating of 40 (scale of 0 to 100), after which pain ratings were recorded for initial, middle, and last 2-minute segment. Temporal summation index (TSI) of pain was calculated by performing subtraction of the final pain rating minus the initial pain rating, thus higher scores indicate greater TSI. Self-reported baseline expectancy was assessed with an 11-point Likert scale (from 0 to 10) asking participants: ‘How much do you expect acupuncture treatment will relieve your fibromyalgia pain?’ Brief Pain Inventory (BPI) scores for pain severity were assessed prior to and following treatment and percent change in BPI pain severity (pBPI) was taken as an indicator of treatment effect. Pearson’s correlations between pBPI and baseline temporal summation or expectations were performed separately for EA and ML groups. A General Linear Model (GLM) was constructed to test differences in temporal summation and expectations in predicting pBPI across groups. A Grubb’s test was applied to identify outliers. A p-value < 0.05 was considered significant.

Results: One subject was excluded with an outlying pBPI score. Lower baseline temporal summation was significantly correlated to greater improvements in pain in the EA group (r=0.393, p=0.024) but not ML group (r=-0.21, p=0.218). 15.4% of the change in BPI is accounted for by the baseline temporal summation score (r²=0.154). A GLM showed a significant group X temporal summation interaction with predicting pBPI (b=0.009, SE=0.004, p=0.014). Baseline expectations of acupuncture treatment had no impact on response to EA (r=0.021, p=0.908) or ML (r=0.077, p=0.654) treatment, with a non-significant group X expectations interaction (p >0.50).

Conclusion: This study shows support for using a quantitative sensory testing metric, TSI, but not expectations, to determine optimal acupuncture treatment for fibromyalgia pain. This study suggests that individuals with FM with greater temporal summation of pain may not respond well to EA. In the future, operationalization of point-of-care TSI measures could be implemented to predict responsiveness to acupuncture treatment in fibromyalgia patients treated clinically.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/impact-of-pain-sensitivity-and-expectations-on-predicting-response-to-acupuncture-in-fibromyalgia/