The use of self-report questionnaires to detect characteristics of altered central pain processing, as seen in centralized pain disorders such as fibromyalgia, allow for the epidemiological studies of pain patients. Here, we assessed the relationship between reporting high levels of pain while taking opioids and the presence of characteristics associated with centralized pain.
We evaluated 582 patients taking opioid medications using validated measures of clinical pain, neuropathic pain symptoms, mood, and functioning. A multivariate linear regression model was used to assess the association between levels of pain while taking opioids and presenting with characteristics consistent with having centralized pain.
We found that 49% of patients taking opioids continued to report severe pain (≥ 7/10). In multivariate analysis, factors associated with having higher levels of pain in opioid users included higher fibromyalgia survey scores (P = 0.001), more neuropathic pain symptoms (P < 0.001), and higher levels of depression (P = 0.002). Although only 3.2% were given a primary diagnosis of fibromyalgia by their physician, 40.8% met American College of Rheumatology survey criteria for fibromyalgia.
Our findings suggest that patients with persistently high pain scores despite opioid therapy are more likely than those with lower levels of pain to present with characteristics associated with having centralized pain. This study cannot determine whether these characteristics were present before (fibromyalgia-like patient) or after the initiation of opioids (opioid-induced hyperalgesia). Regardless, patients with a centralized pain phenotype are thought to be less responsive to opioids and may merit alternative approaches.
From the Departments of *Anesthesiology and †Biostatistics, University of Michigan, Ann Arbor, MI.
Accepted for publication September 24, 2013.
Address correspondence to: Ronald A. Wasserman, MD, FRCPC, University of Michigan Back and Pain Center, Burlington Bldg 1, Floor 1, 325 E. Eisenhower Parkway, Ann Arbor, MI 48108 (e-mail: firstname.lastname@example.org).
Dr Brummett is a consultant for Purdue Pharma (Stamford, CT). Dr Hassett receives research funding from and has been a consultant for Bristol-Myers Squibb (New York, NY) and Pfizer (New York, NY). The other authors declare no conflict of interest.
This study was supported by the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, MI.
Preliminary data presented at the American Society of Regional Anesthesia and Pain Medicine Fall Meeting, New Orleans, LA, November 17, 2011.