Clinical Characteristics of Fibromyalgia in a Chronic Pain Population.

OBJECTIVE: To compare fibromyalgia (FM) characteristics among patients identified in a community-based chronic pain cohort based on traditional International Classification of Diagnoses 9th revision (ICD-9) diagnostic coding, with that of patients identified using a novel predictive model. METHODS: This retrospective study used data collected from July 1999 to February 17, 2015, in multiple chronic pain clinics in the United States. Patients were assigned to the FM case group based on specific inclusion criteria using ICD-9 codes or, separately, from results of a novel FM predictive model that was developed using random forest and logistic regression techniques. Propensity scoring (1:1) matched FM patients (cases) to nonmalignant chronic pain patients without FM (controls). Patient-reported measures (eg, pain, fatigue, quality of sleep) and clinical characteristics (ie, comorbidities, procedures, and regions of pain) were outcomes for analysis. RESULTS: Nine ICD-9 clinical modification diagnoses had odds ratios with large effect sizes (Cohen's d > 0.8), demonstrating the magnitude of the difference between the FM and matched non-FM cohorts: chronic pain syndrome, latex allergy, muscle spasm, fasciitis, cervicalgia, thoracic pain, shoulder pain, arthritis, and cervical disorders (all P < 0.0001). Six diagnoses were found to have a moderate effect size (Cohen's 0.5 < d > 0.8): cystitis, cervical degeneration, anxiety, joint pain, lumbago, and cervical radiculitis. CONCLUSIONS: The identification of multiple comorbidities, diagnoses, and musculoskeletal procedures that were significantly associated with FM may facilitate differentiation of FM patients from other conditions characterized by chronic widespread pain. Predictive modeling may enhance identification of FM patients who may otherwise go undiagnosed.

Interpreting the Effectiveness of Opioids and Pregabalin for Pain Severity, Pain Interference, and Fatigue in Fibromyalgia Patients.

OBJECTIVE: To evaluate the effectiveness of opioids and/or pregabalin on patient-reported outcomes among fibromyalgia (FM) patients based on levels of improvement. METHODS: A total of 1,421 FM patients were identified, with 3,082 observational periods of opioids with or without pregabalin use between April 2008 and February 2015. Patients were categorized by opioids, and pregabalin with and without opioids; opioids were designated by morphine equivalent dose (MED) of ≤ 20 (low MED), > 20 to < 100 (moderate MED), ≥ 100 (high MED), and pregabalin doses of ≤ 150 mg, 151 to 300 mg, and 301 to 450 mg. Proportions of patients meeting clinically relevant thresholds of ≥ 30% and ≥ 50% improvement for pain interference (ability to enjoy life; activity; mood; relationships; sleep), pain severity, and fatigue were compared among treatments, and area under the curve (AUC) for improvement and worsening of effects was determined, enabling ranking of treatments. Further analysis compared pregabalin doses. RESULTS: Pregabalin without opioids resulted in the highest proportions of patients with ≥ 30% improvement on all pain items and pain interference with "ability to enjoy life," "activity" "mood," and "sleep." For the ≥ 50% threshold, pregabalin alone was highest for all pain interference items and for "average pain" and "worst pain." Pregabalin was consistently lowest across thresholds for fatigue, but showed better results combined with moderate MED opioids. Pregabalin doses recommended for treatment of FM (151 to 450 mg) generally resulted in the highest proportion of patients achieving thresholds relative to opioids. The AUC results were consistent with thresholds; pregabalin without opioids resulted in the greatest benefits with regard to improvement, with the highest ranking for overall improvement and overall effects. CONCLUSION: Pregabalin without opioids provided the most favorable outcomes overall based on ≥ 30% and ≥ 50% improvement thresholds and AUC, with support for moderate MED opioids + pregabalin in patients suffering from fatigue. While most patients took less than recommended pregabalin doses, higher doses may lead to improved outcomes.