The new criteria are published in the May issue of the ACR journal Arthritis Care & Research.

"These new criteria recognize that fibromyalgia is more than just body pain," said Robert S. Katz, one of the authors of the new criteria and a rheumatologist at Rush University Medical Center. "This is a big deal for patients who suffer symptoms but have had no diagnosis. A definite diagnosis can lead to more focused and successful treatment and reducing the stress of the unknown."

Routine lab tests can not detect fibromyalgia, a condition that is characterized by unexplained pain from head to toe and exhaustion. Instead, the diagnosis has been made by a tender point test, a physical exam that focuses on 18 points throughout the body. When light pressure is applied to these points, clustered around the neck, shoulder, chest, hip, knee, and elbow regions, patients with fibromyalgia feel tenderness or pain.

To meet the previous diagnostic criteria, which were established in 1990, patients must have widespread pain in all four quadrants of their body for a minimum duration of three months and experience moderate pain and tenderness at a minimum of 11 of the 18 specified tender points.

"There are numerous shortcomings with the previous criteria, which didn't take into account the importance of common symptoms including significant fatigue, a lack of mental clarity and forgetfulness, sleep problems and an impaired ability to function doing normal activities," said Katz.

According to Katz, fibromyalgia pain may fluctuate, which can affect the number of tender points, and the tender point test did not adequately measure symptom severity or the effectiveness of new treatments.

"The tender point test also has a gender bias because men may report widespread pain, but they generally aren't as tender as women. Fibromyalgia may be under-diagnosed in both men and women because of the reliance on 11 tender points, and also due to failing to account for the other central features of the illness," said Katz.

Additionally, due to the confusion regarding the tender point test, the authors note that most primary care doctors don't bother to check tender points or they aren't checking them correctly. Consequently, fibromyalgia diagnosis in practice has often been a symptom-based diagnosis. The new criteria will standardize a symptom-based diagnosis so that all doctors are using the same process.

The tender point test is being replaced with a widespread pain index and a symptom severity scale. The widespread pain index score is determined by counting the number of areas on the body where the patient has felt pain in the last week. The checklist includes 19 specified areas.

The symptom severity score is determined by rating on a scale of zero to three, three being the most pervasive, the severity of three common symptoms: fatigue, waking unrefreshed and cognitive symptoms. An additional three points can be added to account for the extent of additional symptoms such as numbness, dizziness, nausea, irritable bowel syndrome or depression. The final score is between 0 and 12.

To meet the criteria for a diagnosis of fibromyalgia a patient would have seven or more pain areas and a symptom severity score of five or more; or three to six pain areas and a symptom severity score of nine or more.

Some criteria will remain unchanged. The symptoms must have been present for at least three months, and the patient does not have a disorder that would otherwise explain the pain.

To develop and test the new criteria, researchers performed a multicenter study of 829 previously diagnosed fibromyalgia patients and a control group of rheumatic patients with non-inflammatory disorders using physician physical and interview examinations. The data were processed by the National Data Bank for Rheumatic Diseases.

The authors note the study has a number of limitations. They recommend a follow-up test in the primary care setting that includes patients with other rheumatic conditions to determine the rate of misclassification that may occur.

The study was funded by Lilly Research Laboratories. Lilly Research Laboratories did not participate in the design of the study, see the results of the study, or review the manuscript or submitted abstracts.

Note: If no author is given, the source is cited instead.

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