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Fibromyalgia: diagnosis and treatment

Background
Diagnosing fibromyalgia
Antidepressants for fibromyalgia
Results
Comment

Readers who dart to this article in the hope that someone has cracked the problem are going to be disappointed. Those fortified with some Scottish medicine may have the strength to read a little about diagnostic difficulty and therapeutic back-up.

Background


Fibromyalgia, for Bandolier , has been a bit like calcium metabolism. You know it's there. You know that it's important, but time is somehow never quite right to turn one's brain on and get stuck in. On the whole, we'd rather be in Philadelphia.

The trouble is that there's a lot of fibromyalgia around. About 10% of the population may have chronic widespread pain, with the more serious diagnosis of fibromyalgia in 1-2% or so, but more in people over 60. That's getting on for 10,000 and 2,000 patients respectively for an average Primary Care Group of 100,000 people. Diagnosis is difficult and treatments limited.

Diagnosing fibromyalgia


The American College of Rheumatology has produced diagnostic guidelines. The historical feature of fibromyalgia is widespread pain of three months duration or more affecting the axial skeleton and at least two contralateral quadrants of the body. In addition, for a diagnosis of fibromyalgia patients have to feel pain in 11 of 18 trigger points when they are palpated with the amount of pressure sufficient to blanch a finger nail.

How useful are trigger points? Tricky territory this, because large data sets seem to be lacking. In Cheshire, 250 subjects selected from participants in a chronic pain survey were asked to undergo a trigger point examination [1]. Of the 250, 100 had chronic widespread pain, 100 regional pain and 50 no chronic pain in the survey. On the day of examination, pain state in these patients had shifted. For instance 3/74 with stated chronic widespread pain now had no pain, and 7/39 with no chronic pain now had chronic widespread pain.

According to their status on the day of examination, the criterion of 11 of 18 painful trigger points was found in 40% of patients with chronic widespread pain, 20% of those with regional pain and 5% of those with no pain (Figure 1). Overall 20 of 132 patients without one of the two criteria of fibromyalgia had at least 11 painful trigger points. By contrast 29% of patients with chronic widespread pain had only 0-4 painful points.

Figure 1: Trigger points in chronic widespread pain, regional pain and no pain



The criterion of eleven painful trigger points looks a poor diagnostic bet. The problem with assessing painful trigger points are several. There is no gold standard against which they can be measured. Experts elicit different numbers [2] in the same patients. Again, perhaps an all or nothing approach to fibromyalgia (with or without trigger points) hides a wider spectrum of disease.

Antidepressants for fibromyalgia


Readers should be looking forward to a feast when they hear that three meta-analyses have been published in recent years [3-5]. Unfortunately these only serve up a light snack. Partly that is to do with the raw materials, in that trials have been often small (most with 6-47 patients), some have had poor diagnostic criteria, and many report outcomes in ways that are unhelpful. Partly, though, it's to do with the way that the raw materials have been combined. Only one review [3] tells us about the reporting quality and validity of the trials being combined, making the others somewhat less than useful except as a source of references.

What can be said is that antidepressants have been used for treating fibromyalgia successfully [3]. Quality in 13 included trials was good, initial diagnosis predominantly used American College of Rheumatology criteria or its equivalent, and that outcomes were sensibly reported in most.

Results


To improve the symptoms of one patient with fibromyalgia, we have to treat four (95%CI 2.9 to 6.3) with antidepressants rather than placebo. Improvements for fatigue, sleep, overall well-being and pain were significant and moderate using effect sizes. Painful trigger points were not improved.

Comment


There's no neat answer here, only more questions. We use the criterion of 11 painful trigger points to define fibromyalgia, but the most successful treatment does not change the number of trigger points. It helps pain, sleep and other symptoms, and maybe patient and physician assessment of problems, but not the diagnostically defining criterion.

This is food for thought, that meta-analysis of treatment studies can help the understanding of diagnosis. The evidence for the usefulness of trigger points is thin. The evidence that antidepressants help is moderate. But we still don't know what dose of what drug is best for whom, or what we are treating in a disorder that may affect a lot of us. Great when things come together, isn't it?

References:

  1. P Croft et al. Population study of tender points counts and pain as evidence of fibromyalgia. BMJ 1994 309: 696-699.
  2. F Wolfe et al. The fibromyalgia and myofascial pain syndromes: a preliminary study of tender points and trigger points in persons with fibromyalgia, myofascial pain syndrome and no disease. Journal of Rheumatology 1992 19: 944-951.
  3. PG O'Malley et al. Treatment of fibromyalgia with antidepressants: a meta-analysis. Journal of General Internal Medicine 2000 15: 659-666.
  4. LM Arnold et al. Antidepressant treatment of fibromyalgia: a meta-analysis and review. Psychosomatics 2000 41: 104-113.
  5. LA Rossy et al. A meta-analysis of fibromyalgia treatment interventions. Annals of Behavioural Medicine 1999 21: 180-191.
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