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
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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:
- P Croft et al. Population study of tender points counts and pain as
evidence of fibromyalgia. BMJ 1994 309: 696-699.
- 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.
- PG O'Malley et al. Treatment of fibromyalgia with antidepressants: a
meta-analysis. Journal of General Internal Medicine 2000 15: 659-666.
- LM Arnold et al. Antidepressant treatment of fibromyalgia: a meta-analysis
and review. Psychosomatics 2000 41: 104-113.
- LA Rossy et al. A meta-analysis of fibromyalgia treatment interventions.
Annals of Behavioural Medicine 1999 21: 180-191.
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