At this time, there is no specific test that can be used to diagnose fibromyalgia. The syndrome is usually diagnosed by documenting the patient's medical history, ruling out disorders and diseases that may be mimicking or exacerbating fibromyalgia, and by utilizing the criteria developed by the American College of Rheumatology (ACR) in 1990. These criteria include:
- A history of widespread chronic pain for at least three months in all four body quadrants – right and left upper body and right and left lower body; pain in the axial skeleton (cervical, down the spine, and/or in the chest)
- Pain in 11 of 18 tender points, as measured by palpation using a 4 kg (9 pound) force [Illustration of tender point locations; test must be performed by a trained professional]
The ACR criteria were originally developed to guide fibromyalgia research, and there is some controversy in using them clinically. Because a patient's symptoms may vary and may come and go, a person may not meet the criteria at the time they are initially tested. Partially because of this, in 2010 a modification to the diagnostic criteria was proposed and provisionally accepted by the ACR. The proposed diagnostic criteria evaluate pain location and severity but are less focused on specific tender points. A person would be considered to have fibromyalgia if they met the following:
- Using a widespread pain index (WPI) and a symptom severity (SS) scale, a person has a WPI of ≥ 7 and SS ≥ 5, or WPI 3-6 and SS ≥ 9.
- Symptoms that have been present at a similar severity level for at least 3 months.
- The person does not have another disorder that would explain the pain.
Additional data must be gathered before the ACR considers accepting these criteria as a replacement for the 1990 criteria. In the meantime, doctors generally consider the results of their evaluations in conjunction with other findings.
Laboratory tests can be useful to help diagnose conditions with symptoms similar to fibromyalgia and to identify disorders that may be coexisting with fibromyalgia, such as rheumatoid arthritis, Sjögren syndrome, thyroid disease, and lupus. It is not usually cost effective or necessary to do extensive screening. General tests that may be ordered include:
- CMP (Comprehensive Metabolic Panel) – to examine electrolytes, proteins, liver and kidney function, calcium, and glucose
- CBC (Complete Blood Count) – to look for anemia, white and red blood cell abnormalities
- TSH (Thyroid Stimulating Hormone) and/or other thyroid testing as hypothyroidism can cause symptoms similar to fibromyalgia
- ANA (Anti-nuclear antibody) - to rule out autoimmune disorders
- CK (creatine kinase) - to rule out other conditions that can cause muscle weakness or pain
Your doctor will consider the results of the general tests, your history (including family history and risk factors for certain diseases), and the results of your physical examination. Based on these findings, some additional tests could be done.
Some very specialized laboratory tests, such as the measurement of Substance P (a neurochemical that signals the brain to register pain), may be used in a research setting to attempt to better understand the cause and course of fibromyalgia, but they are not considered clinically useful at this time.
An electromyograph (EMG) may be performed to evaluate someone with symptoms associated with fibromyalgia. The test assesses the health of muscles and the nerves that control them. For more on this procedure, read the Electromyograph article on the Mayo Clinic web site.
Occasionally, an imaging scan may be ordered to help rule out a disorder that is causing symptoms similar to fibromyalgia, such as an MRI (magnetic resonance imaging) to help identify multiple sclerosis.