New developments in the diagnosis of fibromyalgia syndrome: Say goodbye to tender points?
ABSTRACTThe Symptom Intensity Scale score can be used to identify and quantify fibromyalgia syndrome from information supplied by a simple questionnaire. In this paper, the author describes how this test was developed and argues in favor of its use in clinical practice in diagnosing fibromyalgia syndrome.
KEY POINTS
- The Symptom Intensity Scale questionnaire consists of two parts: a list of 19 anatomic areas in which the patient is asked if he or she feels pain (the total number of yes answers being the Regional Pain Scale score), and a visual analogue scale for fatigue.
- According to the Survey Criteria, a diagnosis of fibromyalgia can be entertained if the Regional Pain Scale score is 8 points or higher and the fatigue visual analogue scale score is 6 cm or higher.
- The number of tender points, a surrogate for diffuse pain, does not fully capture the essence of fibromyalgia syndrome, in which accompanying fatigue is often severe and nearly always present.
- The Symptom Intensity Scale is an accurate surrogate measure for general health, depression, disability, and death. Fibromyalgia syndrome diagnosed with this instrument implies that this illness carries increased medical risk.
It can detect fibromyalgia syndrome in patients with other diseases
Not surprisingly, distress-related fibromyalgia syndrome is more common in patients with chronic rheumatic or arthritic diseases, with a frequency ranging from 5% in osteoarthritis to 47% in Sjögren syndrome.1 When present, fibromyalgia syndrome changes the features of the other disease.
Wolfe and Michaud32 used the Survey Criteria to evaluate 11,866 rheumatoid arthritis patients and found that 17.1% of them also had fibromyalgia syndrome, and those that did had higher levels of pain, greater global severity, higher scores on the Health Assessment Questionnaire and Short Form-36 mental component, and more disability than those without fibromyalgia syndrome.
Urrows et al33 found that the mean tender-joint count correlated with the mean tenderpoint count in 67 patients with rheumatoid arthritis followed for 75 days. Comorbid fibromyalgia syndrome rendered joints more tender, so that an examiner using the tender-joint count as a major indicator of disease severity might overestimate severity and excessively treat a rheumatoid arthritis patient with unrecognized concurrent fibromyalgia syndrome. Because comorbid fibromyalgia syndrome can inflate Health Assessment Questionnaire scores and subjective pain scale scores in rheumatoid arthritis, more appropriate investigation and management decisions should follow recognition.
Concurrent fibromyalgia syndrome can also be troublesome in SLE. Patients with fibromyalgia syndrome had greater disability than patients without fibromyalgia syndrome despite having no worse SLE damage scores.29 Comorbid fibromyalgia syndrome in SLE has also been shown to diminish quality of life as measured by the Short Form-36.34
Fibromyalgia syndrome also has the potential to confound the diagnosis of concomitant diseases. Wolfe et al35 found that 22.1% of 458 patients with SLE also had fibromyalgia syndrome using the Symptom Intensity Scale criteria. At the time of referral to a rheumatologist, patients who met the criteria for fibromyalgia syndrome were more likely to have self-reported a diagnosis of SLE than were patients for whom SLE had been previously physician-confirmed. The authors warned that fibromyalgia syndrome could intrude into the precision of the diagnosis if only a positive antinuclear antibody test and “soft” SLE criteria were used for diagnosis. If we are unaware of fibromyalgia syndrome, spurious diagnoses may ensue.
BOTTOM LINE
I use the Symptom Intensity Scale as part of routine evaluation in my office. Most patients can complete it with no instruction in 2 minutes or less. I believe it should be used in the clinic to confirm a diagnosis of fibromyalgia syndrome in patients with chronic diffuse pain at rest and to identify comorbid distress in patients with other diseases. This test complements a careful patient history and physical examination, and through its symptom and general health correlations facilitates characterization of our patients’ illnesses in line with the biopsychosocial model.
Since the Symptom Intensity Scale has been shown to be an accurate surrogate measure for general health, depression, disability, and death, fibromyalgia syndrome diagnosed using this instrument implies that this illness is not just centrally mediated pain, but that it carries increased medical risk. It can also be used as a research tool to measure the prevalence of fibromyalgia syndrome in other diseases.
Although the Symptom Intensity Scale is not yet recognized by the ACR as part (or the whole) of the classification criteria for fibromyalgia syndrome, it has already been shown in published studies to be a valid research tool, and it will very likely be the cornerstone of the new criteria.
Goodbye to tender points? Get used to it.
