Evoked Pressure Pain Sensitivity Is Associated with Differential Analgesic Response to Verum and Sham Acupuncture in Fibromyalgia

Abstract

Objective: Fibromyalgia is a chronic pain condition with few effective treatments. Many fibromyalgia patients seek acupuncture for analgesia; however, its efficacy is limited and not fully understood. This may be due to heterogeneous pathologies among participants in acupuncture clinical trials. We hypothesized that pressure pain tenderness would differentially classify treatment response to verum and sham acupuncture in fibromyalgia patients.

Design: Baseline pressure pain sensitivity at the thumbnail at baseline was used in linear mixed models as a modifier of differential treatment response to sham versus verum acupuncture. Similarly, needle-induced sensation was also analyzed to determine its differential effect of treatment on clinical pain.

Methods and patients: A cohort of 114 fibromyalgia patients received baseline pressure pain testing and were randomized to either verum (N = 59) or sham (N = 55) acupuncture. Participants received treatments from once a week to three times a week, increasing in three-week blocks for a total of 18 treatments. Clinical pain was measured on a 101-point visual analog scale, and needle sensation was measured by questionnaire throughout the trial.

Results: Participants who had higher pain pressure thresholds had greater reduction in clinical pain following verum acupuncture while participants who had lower pain pressure thresholds showed better analgesic response to sham acupuncture. Moreover, patients with lower pressure pain thresholds had exacerbated clinical pain following verum acupuncture. Similar relationships were observed for sensitivity to acupuncture needling.

Conclusions: These findings suggest that acupuncture efficacy in fibromyalgia may be underestimated and a more personalized treatment for fibromyalgia may also be possible.

Keywords: Fibromyalgia; Needling Sensation; Pressure Pain Threshold; Quantitative Sensory Testing; Acupuncture.

Figure 1

Flow of participants in the study. Only patients with complete sensation data were analyzed.

Figure 2

Summary of clinical pain response by treatment (verum and sham) and pressure pain threshold. The relationship between the type of acupuncture (verum vs vham), cumulative dose (number of treatments since washout), and the level (tertile) of pressure pain threshold (category scale on the right; low: 0–1.81 kg; medium: 1.81–3.12 kg; high: 3.12–6.5 kg). Box plots show median line, 25–75th percentile box, and 1.5 interquartile range outliers. Zero dose corresponds to the washout periods. Patients with low pressure pain thresholds respond better to sham but not verum acupuncture. Patients with high pressure pain threshold respond better to verum and not sham acupuncture.

Figure 3

Predicted pain responses. Predicted mean visual analogue scale pain responses in a patient treated by different types of acupuncture and characterized by different pain threshold and sensation levels.