New developments in the diagnosis of fibromyalgia syndrome: Say goodbye to tender points?

Counting tender points

Smythe (1979)¹² was the first to define and classify fibromyalgia syndrome as a rule-in diagnosis. Smythe’s criteria included tender points in at least 12 of 14 anatomic locations using 4 kg of pressure. In practice, the pressure is approximate—the nail bed blanches in a normotensive examiner with a force of 4 kg. He also described four necessary signs and symptoms: diffuse pain of at least 3 months’ duration, disturbed sleep, skin-roll tenderness at the upper trapezius border, and normal results on laboratory tests. He and Moldofsky¹³ also found a relationship between disordered slow-wave sleep and the symptoms of fibromyalgia syndrome.

Yunus et al (1981)¹⁴ compared signs and symptoms in 50 patients with fibromyalgia syndrome and 50 healthy controls to develop criteria for the disease. Of the resulting criteria, two were mandatory: diffuse pain of at least 3 months’ duration and lack of other obvious causes. The definition also required tenderness in at least 5 of 40 tender points and outlined 10 minor criteria.

Signs and factors that modulate fibromyalgia syndrome and that were derived from these minor criteria are still clinically important today. Factors that aggravate pain include cold or humid weather, fatigue, sedentary state, anxiety, and overactivity. Relieving factors include a hot shower, physical activity, warm dry weather, and massage.

The American College of Rheumatology (1990). Understanding that at any one time approximately 15% of the general population experiences widespread pain,¹⁵ a committee of the American College of Rheumatology (ACR) set out to differentiate patients with fibromyalgia syndrome from those with less severe widespread pain. The committee compared signs and symptoms in 293 patients deemed by experts to have fibromyalgia syndrome and 265 control patients matched for age, sex, and concomitant rheumatic disorders. ¹⁶

The symptom of widespread pain of at least 3 months’ duration and tenderness in at least 11 of 18 points became the ACR’s diagnostic criteria and provided a sensitivity of 88% and a specificity of 81% compared with the experts’ opinion as the gold standard test.

Low specificity is one of the recognized problems with the ACR criteria: 19% of patients with at least 11 tender points did not have fibromyalgia syndrome. In addition, tender points don’t correlate well with some measures of illness activity, such as the Fibromyalgia Impact Questionnaire.¹⁷

Is the tender-point count a good measure?

The best argument for continuing to count tender points as part of the clinical evaluation is that it is a measure of severity. Higher numbers of tender points indicate greater psychological distress and greater severity and frequency of other, closely related fibromyalgia symptoms.^18,19 Nearly everyone in the general population has at least a few tender points.¹⁶ In fibromyalgia syndrome, the tender-point count is a good status surrogate, a measure of the state of the illness.

But should a state/status measure be used as an illness trait and a criterion for diagnosis? I believe not. Consider, as an analogy, the use of the erythrocyte sedimentation rate in patients with rheumatoid arthritis. An elevated sedimentation rate may indicate increased systemic inflammation, but it is a measure of the status of rheumatoid arthritis, not a trait of this disease. This is why I believe that most rheumatologists would disagree with using some value of the erythrocyte sedimentation rate as a criterion for the diagnosis of rheumatoid arthritis and, by analogy, the tender-point count as a criterion for the diagnosis of fibromyalgia syndrome. Also, the number of tender points, a surrogate for diffuse pain, does not fully capture the essence of the illness, in which accompanying fatigue is often severe and nearly always present.²⁰

A CONTEMPORARY DEFINITION AND ITS VALIDATION

As the concept of fibromyalgia syndrome evolved, a movement away from tender points took hold.²¹

The Manchester criteria²² used a pain diagram to establish the diagnosis, in which the patient indicated the areas of pain on a simple drawing, obviating the need for tender points. It showed good agreement with the ACR criteria, and in fact identified patients with more severe symptoms.

The London Fibromyalgia Epidemiology Study Screening Questionnaire,²³ designed as an epidemiologic tool to estimate the prevalence of the syndrome, was the first test to specifically include both pain and fatigue.

White et al,²⁴ in a very important subsequent study, showed that higher fatigue scores differentiated patients with widespread pain and only a few tender points (7–10) from those with more tender points. This report helped to set the stage for the Symptom Intensity Scale.

What the Symptom Intensity Scale measures

• The Regional Pain Scale score, which is the number of anatomic areas—out of a possible 19—in which the patient feels pain
• A fatigue visual analogue scale score, in which the patient makes a mark somewhere along a 10-cm line to indicate how tired he or she feels. Subsequently, the clinician measures the position of the mark from the left end of the line with a ruler.