Background/Purpose: The study’s purpose was to advance the understanding and treatment of fibromyalgia (FM) for patients in a chronic pain management center.  FM is a chronic disorder that causes widespread musculoskeletal pain and fatigue, as well as a number of other symptoms. FM pain ranges from mild to incapacitating.   Given the many possible co-morbidities associated with FM, we set out to examine clinical characteristics of FM patients compared with those with chronic pain but without FM.  We did this to identify and better match patients to appropriate therapy.

Methods: This was a retrospective study with a case-control design based on data collected from July 1999 to February 17, 2015 in multiple chronic pain clinics in the United States. Patients were assigned to the case group of FM patients based on specific inclusion criteria. Propensity-score 1:1 matching was used to match controls (non-malignant chronic pain patients without FM) to cases based on identified confounders.  A final sample of 1,070 controls and 1,069 cases was obtained to investigate co-morbidities, procedures, and regions of pain associated with FM.  Items from a pain health assessment were also used to investigate patient-reported measures such as impairment, pain, fatigue, and quality of sleep.  Pearson’s chi-square and odds ratios were used to assess the significance and magnitude of relationships, two-sample t-tests were used for patient procedures, and a mixed model with repeated measures was implemented for patient-reported outcomes.  Confidence intervals and effect sizes were included for each individual analysis.

Results: Nine additional International Classification of Diseases, Clinical Modification (ICD–9-CM) diagnoses were found to have odds ratios with large effect sizes (Cohen’s d > 0.8).  These diagnoses included chronic pain syndrome, latex allergy, muscle spasm, fasciitis, cervicalgia, thoracic pain, shoulder pain, rheumatoid arthritis, and cervical disorders (all p < 0.0001).  Six diagnoses were found to have a moderate effect size (Cohen’s d > 0.5): cystitis, cervical degeneration, anxiety, joint pain, lumbago, and cervical radiculitis.  Current Procedural Terminology (CPT) procedure codes for musculoskeletal pain, specifically, trigger point injections, were shown to be used to treat FM cases in 5.9 more instances than controls, on average.  There was insufficient evidence to suggest that patient-reported items from the pain health assessment were significantly different between cases and controls.

Conclusion: Multiple co-morbidities, diagnoses, and procedures were associated with FM patients in this study.  Pain management physicians are uniquely positioned to treat FM patients.  When coding procedural work they are driven by billing codes associated with each procedure and sometimes miss the fact they are dealing with a FM patient.  Our goal is develop an alert system of diagnoses and procedures that would help doctors in differentiating FM patients from other painful conditions.  Doing so is more practical and realistic than the current symptom severity scale and widespread pain index, both of which are rarely obtained in the pain management clinical setting.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-characteristics-of-fibromyalgia-in-a-chronic-pain-population/