Outcome and Predictor Relationships in Fibromyalgia and Rheumatoid Arthritis
A recent article suggests that Fibro is part of a continuum of severity, rather than a discrete condition.
The study aimed to compare outcome-predictor relationships in Fibromyalgia Syndrome (Fibro) and Rheumatoid Arthritis (RA), in order to provide information regarding the competing hypotheses that: 1, Fibro is a continuum; or 2, that Fibro is a discrete disorder.
The researchers studied 3 outcome variables (work disability, opioid use, depression) and 12 clinical predictor variables in 2,046 patients with Fibro and 20,374 with RA.1
They determined whether outcome predictor relationships were stronger in the Fibro patient group or in the RA patient group by measuring the areas under the receiver-operating curves. The researchers also used fractional polynomial logistic regression to create graphic models for the outcome-predictor relationships.1
All measures of status and outcome measured in the study were more abnormal in the Fibro patient group than in the RA patient group.1
Depression was reported in 33.4% of patients with Fibro compared with 15.1% of those with RA.1
The predictor-outcome relationship was significantly stronger in RA in 28 of the 36 tests, and not different in the remainder. The relationship between outcome and predictor variables was generally similar in patients with Fibro and RA. However, unmodeled depression that was not explained by study variables was noted in the Fibro patient group.1
The article concludes that:
"Our data are consistent with the hypothesis that [FIbromyalgia Syndrome] is the end of a severity continuum, but that additional psychological factors are an integral part of the syndrome."1
Some of the worlds top Fibro researchers have previously suggested that Fibro is at the end of the spectrum of chronic pain disorders or central sensitivity syndromes2 3. It has also been suggested that there isn't a clear defining line between people with Fibro and people without Fibro, but a continuum of people with varying degrees of pain, hypersensitivity to pain, symptoms of central sensitivity (e.g. migraine, Irritable Bowel Syndrome) and non-restorative sleep and it is only the severe end of this continuum that can be diagnosed with Fibro2 4.
- Wolfe F, Michaud K. Outcome and Predictor Relationships in Fibromyalgia and Rheumatoid Arthritis: Evidence Concerning the Continuum versus Discrete Disorder Hypothesis. J Rheumatol. 2009 Feb 17. [Epub ahead of print]
- Clauw DJ. Mechanistic studies and their implication for the Management of Fibromyalgia Syndrome. J Musc Pain. 2008. Vol 16, 1/2: 59-66
- Yunus MB. Fibromyalgia and Overlapping Disorders: The Unifying Concept of Central Sensitivity Syndromes. Semin Arthritis Rheum. 2007 Jun;36(6):339-56. Epub 2007 Mar 13. Review.
- Fibromyalgia in 2009: A lecture by Andrew Holman MD. 2009. [DVD] UK: FibroAction. (Available on application to FibroAction).