To the Editors:

We thank Drs. Thompson, Vanderschueren, Staud, and colleagues for their comments on the new diagnostic criteria for fibromyalgia. We note that Dr. Thompson finds the ACR 2010 criteria problematic because she feels there can be confusion between fibromyalgia and MPS, when the latter affects several body regions. It seems unavoidable that disorders that affect muscle might cause confusion with fibromyalgia. However, as noted by Dr. Thompson, in the case of MPS there are criteria that exist to define MPS. So ordinarily the 2 disorders should be distinguishable except, of course, if they are both present simultaneously. We hope that clinicians who use diagnoses like fibromyalgia and MPS would apply current diagnostic methods at the time of diagnosis.

We are grateful to Dr. Steven Vanderschueren and colleagues for raising very important questions about our study and criteria. To paraphrase their first point, they indicate that pain is not simple and that criteria that abandon the physical examination may result in poor medical care. We address this point in our criteria article when we state, “Even though the new criteria do not include a physical examination criterion, all of the patients being diagnosed should have a physical examination, which may include examination of tender point sites…It is important for physicians to perform an appropriate clinical assessment to exclude other diagnoses, and/or to identify potential coexisting rheumatic diseases that may require treatment themselves.” For clinical assessment, we would include some measure of tenderness or pain threshold, but not necessarily a formal tender point count.

Where Vanderschueren et al indicate that “the article clearly shows that the tender point count is the most reliable feature to differentiate fibromyalgia and nonfibromyalgia patients,” we would respond that it is true, of course, because we used the 1990 criteria (1) as a gold standard. That does not mean that tender points are better than other methods; it merely means that they represented the gold standard test for the criteria development. There are substantial issues with the reliability of the tender point examination.

In their second point, Vanderschueren et al state, “The new diagnostic criteria, as opposed to the ACR 1990 classification criteria, implicitly state that fibromyalgia should be a diagnosis of exclusion, without detailing what painful disorders should be ruled out or what tests should be performed for that reason. In contrast, the 1990 classification criteria made no exclusions for the presence of concomitant radiographic or laboratory abnormalities and abandoned the distinction between primary fibromyalgia and secondary-concomitant fibromyalgia.” We think that Vanderschueren and colleagues have misinterpreted our discussion of exclusionary diagnoses. As a study exclusion criterion, we wrote, “The patient does not have a disorder that would otherwise explain the pain,” and we indicated that “implicit in the 1990 ACR classification criteria was the requirement that clinical examination and clinical judgment had excluded other causes of chronic widespread pain, and such an exclusion is also implicit in the proposed diagnostic criteria.” Most of us, for example, would not exclude other rheumatic diseases.

Vanderschueren and colleagues make their third point by saying, “The control group consisted of patients with noninflammatory painful rheumatic disorders. The proportion of control persons with a fibromyalgia diagnosis increased >4-fold (from 2.0% using the 1990 criteria to 9.1% using the new criteria).” We believe this is not correct. The false-positive rate in the 1990 criteria was 18.9% (1). In this third point Vanderschueren and colleagues also wonder whether abandoning the tender point count will open “Pandora's Box.” If we understand Vanderschueren et al correctly, they are worried about misdiagnosis, i.e., calling other conditions fibromyalgia that are really not fibromyalgia. This question really goes to the heart of what fibromyalgia means in the presence of other illnesses. Perhaps some of the patients Vanderschueren and colleagues are worried about should be classified as fibromyalgia patients. We would also point out the strong correlation between the WPI and the tender point count, as shown in Table 3 of the 2010 criteria, and the similar association of both variables with the symptoms we are concerned with. Based on the data from our study, we think it is very unlikely that the new criteria will misclassify many patients.

The fourth point made by Vanderschueren and colleagues is that fibromyalgia patients in this study were older (mean age 54.6 years), suggesting that many had the label for quite some time. In a recent population study, the mean age of fibromyalgia patients was 48.9 years (2). If age is a random variable, we expect age to vary from sample to sample. Even so, age made no difference in the results of our study. In response to the point made by Vanderschueren and colleagues that “a fair share of subjects ended up in the ‘prior fibromyalgia’ category,” we would have to observe that “prior” doesn't reflect age, but rather reflects diagnostic change.

In their fifth point, Vanderschueren et al are concerned that “many patients (36.4%) entering the present study as fibromyalgia patients were labeled as such not based on the ACR classification criteria, but on the personal judgment of the study physician.” The choice to allow patients who were diagnosed without ACR criteria was deliberate. In attempting to slightly change the case definition of fibromyalgia, we wanted to know how rheumatology physicians were defining the disorder. That is, what is the current actual case definition in practice? It has been known from the time of the 1990 criteria that experts might make a diagnosis even when criteria were not satisfied. Vanderschueren et al confuse patients used to make a more valid case definition and the actual criteria that were evaluated against the 1990 criteria. Fibromyalgia can be a difficult problem. We believe that we have scientifically addressed the case definition and found the best criteria for the condition.

If we understand what seems to be Dr. Staud's main point correctly, that we omitted “well-known mechanistic FM features, such as hyperalgesia, central sensitization, or dysfunctional pain modulation” from the criteria, we would reply that central sensitization and dysfunctional pain modulation are not features that can be reasonably assessed in the clinic, and that the widespread pain index provides a measure of hyperalgesia that, as the data show, is equivalent to the tender point count.

With respect to the symptom list, Dr. Staud is mistaken about not reporting the predictive value of the symptoms. We do report the importance of the symptoms in Figure 2, and in importance order. Dr. Staud may assume that variables not in the figure do not contribute to classification.

Dr. Staud writes that we “promote new diagnostic criteria that are almost as good (80% correct classification) as the previous criteria.” This is not correct. Table 5 shows that among patients satisfying ACR 1990 criteria, 88.1% satisfied 2010 criteria in phase 1 and 95.2% in phase 2. In addition, when all patients are considered, not just ACR 1990 positive patients, we wrote in the text, “It should be remembered that physician diagnosis only correctly classified 84.1% of cases, while the proposed diagnostic criteria, even with shift of definition, identified 82.6% of patients correctly.”

Dr. Staud writes, “They [the criteria] also subscribe to the same circular logic as the 1990 ACR criteria.” He should reread the paragraph in the discussion beginning with, “Readers might wonder: why is it so difficult to make new fibromyalgia criteria? The central problem in fibromyalgia criteria is the absence of a gold standard or case definition.” Later in the paragraph we point out that, “In the current study, we derived an empirical case definition from the variable importance analyses.”

If Dr. Staud is not satisfied with the new criteria, he may continue to use the old ones (the ones he criticized for being circular). But one advantage to the new criteria that warrants mentioning is that the change in the case definition demands that the patient's symptoms be paid attention to. Who would want less?

  • 1
    Wolfe F, Smythe HA, Yunus MB, Bennett RM, Bombardier C, Goldenberg DL, et al. The American College of Rheumatology 1990 criteria for the classification of fibromyalgia: report of the Multicenter Criteria Committee. Arthritis Rheum 1990; 33: 16072.
  • 2
    Hauser W, Schmutzer G, Brahler E, Glaesmer H. A cluster within the continuum of biopsychosocial distress can be labeled “fibromyalgia syndrome”: evidence from a representative German population survey. J Rheumatol 2009; 36: 280612.

Frederick Wolfe MD*, Daniel J. Clauw MD†, Mary-Ann Fitzcharles MB, ChB‡, Don L. Goldenberg MD§, Winfried Häuser MD¶, Robert S. Katz MD**, Philip Mease MD††, Anthony S. Russell MD‡‡, I. Jon Russell MD, PhD§§, John B. Winfield MD¶¶, * National Data Bank for Rheumatic Diseases and University of Kansas School of Medicine, Wichita, KS, † University of Michigan Medical School, Ann Arbor, MI, ‡ Montreal General Hospital and McGill University, Montreal, Quebec, Canada, § Newton-Wellesley Hospital and Tufts University School of Medicine, Boston, MA, ¶ Technische Universität München, Munich, Germany, ** Rush University Medical Center, Chicago, IL, †† Seattle Rheumatology Associates and Swedish Medical Center, Seattle, WA, ‡‡ University of Alberta, Edmonton, Alberta, Canada, §§ University of Texas Health Sciences Center, San Antonio, TX, ¶¶ University of North Carolina, Chapel Hill, NC.