Classification criteria should never replace clinical acumen
Opioid responsiveness
To examine whether fibromyalgia survey results correlate with outcomes after knee and hip arthroplasty, Dr. Clauw and colleagues conducted a prospective, observational cohort study that included approximately 500 people. Patients completed the questionnaire on the day of surgery.
Patients with higher levels of fibromyalgia were less responsive to opioids. “For each 1-point increase in the fibromyalgia score, people needed about one more hydrocodone tablet in the first 24-48 hours to control their pain,” he said (Anesthesiology. 2013 Dec;119[6]:1434-43). In addition, each 1-point increase in the fibromyalgia score made people about 25% less likely to have a 50% improvement in knee pain level after 6 months (Arthritis Rheumatol. 2015 May;67[5]:1386-94). The correlations were independent of psychological factors. In addition, the associations were linear. “There was nothing magical about a fibromyalgia score of 13,” Dr. Clauw said.
Dr. Clauw is a coauthor of a study to be presented at the 2019 American College of Rheumatology/Association of Rheumatology Professionals annual meeting that found pain centralization in patients with RA is associated with poor response to disease-modifying antirheumatic drugs (DMARDs).
Prior studies in patients with RA have found that the degree of fibromyalgia is a better predictor of pain and disability than erythrocyte sedimentation rate or the number of swollen joints.
Diagnosed cases are the “tip of the iceberg”
Researchers at Dr. Clauw’s institution have identified dozens of patients undergoing knee surgery who met criteria for fibromyalgia but had not received the diagnosis. “This is at the University of Michigan, which is the epicenter for fibromyalgia research. If we are not seeing fibromyalgia superimposed on OA in our patients, no one is seeing it,” he said.
Patients with diagnosed fibromyalgia are “the tip of the iceberg,” he said. “There are far greater numbers of individuals whose primary diagnosis is OA, RA, lupus, ankylosing spondylitis, cancer pain, or sickle cell disease that have the same fundamental problem as fibromyalgia patients. But you do not see it because you label them as having an autoimmune disease or osteoarthritis. And that is at your peril and at their peril. Because treating that individual as if all of their pain and other symptoms are due to a problem out on the periphery will not make that person better.”
Patients with high levels of centralized pain may be less responsive to peripherally directed therapies such as surgery or injections, Dr. Clauw said. Pharmacologic options for patients with centralized pain include gabapentinoids (e.g., pregabalin and gabapentin), serotonin-norepinephrine reuptake inhibitors (e.g., duloxetine and milnacipran), and tricyclic compounds (e.g., amitriptyline and cyclobenzaprine), he said. “Opioids are going to be quite unlikely to help these individuals,” he said. “In fact, it is likely that opioids will make this kind of pain worse.”
Dr. Clauw is a consultant for Aptinyx, Daiichi Sankyo, Eli Lilly, Intec Pharma, Pfizer, Samumed, Theravance, Tonix, and Zynerba Pharma. He has received grant or research support from Aptinyx and Pfizer and is an expert witness.
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