Research ArticleArticle

Outcome and Predictor Relationships in Fibromyalgia and Rheumatoid Arthritis: Evidence Concerning the Continuum versus Discrete Disorder Hypothesis

FREDERICK WOLFE and KALEB MICHAUD
The Journal of Rheumatology April 2009, 36 (4) 831-836; DOI: https://doi.org/10.3899/jrheum.080897

Article Figures & Data

Figures

  • Figure 1.
    Figure 1.

    Hypothetical model of the distribution of widespread pain (RPS) in fibromyalgia (FM) and non-FM subjects. FM subjects are the actual patients with FM in our study. Non-FM subjects are the study’s patients with rheumatoid arthritis (RA) who have Symptom Intensity Scale scores < 8 (95% of RA subjects). This restriction simulated the distribution of widespread pain in RA with RA patients who had FM removed from the figure.

  • Figure 2.
    Figure 2.

    The relation between work disability and selected predictor variables as determined by fractional polynomial regression. Solid line represents FM, broken line RA. Shaded area represents 95% confidence intervals.

  • Figure 3.
    Figure 3.

    The relation between opioid use and selected predictor variables as determined by fractional polynomial regression. Solid line represents FM, broken line RA. Shaded area represents 95% confidence intervals.

  • Figure 4.
    Figure 4.

    The relation between self-reported depression and selected predictor variables as determined by fractional polynomial regression. Solid line represents FM, broken line RA. Shaded area represents 95% confidence intervals.

Tables

  • Table 1.

    Characteristics of patients with fibromyalgia and rheumatoid arthritis.

    VariableFM, n = 2,046RA, n = 20,374
    MeanSDMeanSD
    Age, yrs57.412.160.513.4
    Sex, % male4.922.8
    Self-reported depression, %33.415.1
    Self-reported depression, lifetime %63.933.0
    Disabled (age < 62 yrs), %30.521.2
    Ordinary opioids, %32.022.9
    Dissatisfied with health, %56.133.4
    VAS QOL0.740.10.780.1
    Sleep disturbance, 0–105.63.03.83.1
    Regional Pain Score, 0–1010.55.55.75.1
    Pain, 0–105.82.64.02.8
    Global severity, 0–104.92.53.72.5
    HAQ, 0–31.30.71.10.7
    Patient activity score, 0–104.92.13.82.3
    Fatigue, 0–106.42.74.53.0
    Symptom intensity scale, 0–105.82.33.72.3
    Comorbidity Index, 0–91.61.41.41.4
    Symptom count, 0–3713.36.67.76.1
    Mental health, SF-3663.621.272.519.1

    • Differences for all variables between groups were significant at p < 0.001. SD: standard deviation; VAS: visual analog scale; QOL: quality of life: HAQ: Health Assessment Questionnaire; SF-36: Medical Outcomes Study Short-Form 36.

  • Table 2.

    Area under the receiver operating curve for outcome predictions in patients with fibromyalgia and rheumatoid arthritis.

    PredictorROC AUC (95% CI)
    Depression    		ROC AUC (95% CI)
    Disabled    		ROC AUC (95% CI)
    Opioid Use
    QOLFM0.648 (0.623, 0.673)*0.700 (0.670, 0.729)*0.594 (0.568, 0.620)
    QOLRA0.666 (0.656, 0.677)*0.724 (0.713, 0.735)*0.654 (0.645, 0.663)
    SleepFM0.618 (0.593, 0.644)0.636 (0.604, 0.668)0.578 (0.551, 0.604)
    SleepRA0.661 (0.650, 0.671)0.689 (0.677, 0.701)0.642 (0.633, 0.651)
    RPSFM0.635 (0.610, 0.660)0.669 (0.638, 0.700)0.605 (0.579, 0.631)
    RPSRA0.685 (0.675, 0.695)0.727 (0.715, 0.738)0.670 (0.661, 0.679)
    PainFM0.644 (0.619, 0.669)0.708 (0.680, 0.737)0.653 (0.628, 0.678)
    PainRA0.685 (0.675, 0.695)0.747 (0.736, 0.757)0.703 (0.694, 0.711)
    GlobalFM0.666 (0.642, 0.690)*0.706 (0.677, 0.735)0.614 (0.588, 0.639)
    GlobalRA0.689 (0.679, 0.699)*0.739 (0.728, 0.750)0.669 (0.661, 0.678)
    HAQFM0.637 (0.612, 0.662)*0.752 (0.726, 0.778)0.635 (0.609, 0.660)
    HAQRA0.659 (0.649, 0.669)*0.802 (0.793, 0.812)0.691 (0.682, 0.699)
    PASFM0.677 (0.652, 0.701)0.760 (0.734, 0.786)0.659 (0.634, 0.684)
    PASRA0.705 (0.695, 0.714)0.797 (0.788, 0.806)0.716 (0.708, 0.724)
    FatigueFM0.656 (0.632, 0.681)0.661 (0.631, 0.691)0.603 (0.577, 0.629)
    FatigueRA0.709 (0.699, 0.718)0.700 (0.688, 0.711)0.664 (0.655, 0.672)
    SI ScaleFM0.674 (0.650, 0.698)0.699 (0.669, 0.728)0.625 (0.599, 0.650)
    SI ScaleRA0.732 (0.723, 0.741)0.748 (0.737, 0.759)0.693 (0.684, 0.701)
    ComorbidityFM0.575 (0.549, 0.600)0.644 (0.613, 0.675)*0.576 (0.550, 0.602)*
    ComorbidityRA0.621 (0.611, 0.632)0.649 (0.636, 0.661)*0.601 (0.592, 0.610)*
    Symptom countFM0.718 (0.695, 0.741)0.688 (0.657, 0.718)*0.628 (0.602, 0.654)
    Symptom countRA0.779 (0.770, 0.787)0.702 (0.690, 0.714)*0.675 (0.666, 0.684)
    MoodFM0.799 (0.779, 0.820)0.665 (0.633, 0.697)*0.576 (0.549, 0.602)
    MoodRA0.827 (0.819, 0.834)0.658 (0.645, 0.671)*0.621 (0.612, 0.631)

    • ↵* = p > 0.05. Sleep: sleep disturbance; QOL: quality of life scale; RPS: Regional Pain Scale; Pain: pain scale; Global: global severity; HAQ: Health Assessment Questionnaire Disability Index; PAS: Patient Activity Scale; Fatigue: fatigue scale; SI: scale: Symptom Intensity scale; Comorbidity: comorbidity index; Mood: SF-36 mental health scale.

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